Method for allocating resources in a wireless communication system and a device for the same

ABSTRACT

A method of transmitting a Relay Physical Downlink Control Channel (R-PDCCH) at a base station in a wireless communication system. A set of Virtual Resource Blocks (VRBs) are assigned for the R-PDCCH to a downlink subframe. The downlink subframe is transmitted to a relay node. The set of VRBs is configured to be same, by higher layer, in a first slot and a second slot of the downlink subframe. If the set of VRBs for the R-PDCCH is assigned in the first slot of the downlink subframe, the R-PDCCH is configured to contain a downlink assignment. If the set of VRBs for the R-PDCCH is assigned in the second slot of the downlink subframe, the R-PDCCH is configured to contain an uplink grant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/640,706 filed on Oct. 11, 2012, which is the National Phase ofInternational Application No. PCT/KR2011/003596 filed on May 16, 2011,which claims the benefit of U.S. Provisional Application No. 61/334,974filed on May 14, 2010; 61/346,010 filed on May 18, 2010; 61/349,210filed on May 28, 2010; 61/350,030 filed on Jun. 1, 2010; 61/356,024filed on Jun. 17, 2010; 61/366,527 filed on Jul. 21, 2010; 61/373,270filed on Aug. 12, 2010. The contents of all of these applications arehereby incorporated by reference as fully set forth herein in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for allocating resourcesfor a physical channel to a relay node.

2. Discussion of the Related Art

Wireless communication systems have been extensively developed toprovide various types of communication services such as a voice or dataservice. Generally, a wireless communication system refers to a multipleaccess system capable of supporting communication with multiple users bysharing available system resources (bandwidth, transmit power, etc.).The multiple access system includes, for example, a Code DivisionMultiple Access (CDMA) system, a Frequency Division Multiple Access(FDMA) system, a Time Division Multiple Access (TDMA) system, anOrthogonal Frequency Division Multiple Access (OFDMA) system, a SingleCarrier Frequency Division Multiple Access (SC-FDMA) system, a MultiCarrier Frequency Division Multiple Access (MC-FDMA) system, etc.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for efficiently allocating resources for a physical channel ina wireless communication system, preferably, in a relay system. It isanother object of the present invention to provide a method andapparatus for efficiently processing a downlink signal.

It will be appreciated by persons skilled in the art that that thetechnical objects that can be achieved through the present invention arenot limited to what has been particularly described hereinabove andother technical objects of the present invention will be more clearlyunderstood from the following detailed description.

According to an aspect of the present invention, A method for handlingdownlink signal by relay in a wireless communication system, the methodcomprising of: receiving a first physical control channel includesresource allocation information for resource block group(RBG); andperforming a process for receiving a physical shared channel from one ormore RBGs indicated by the resource allocation information, wherein theone or more allocated RBGs include a resource block (RB) pair receivedthe first physical control channel, wherein the resource block pair isexcluded from the process for receiving a physical shared channel whenthe second slot of the RB pair is set to a searching space for a secondphysical control channel.

According to other aspect of the present invention, A relay is used in awireless communication system, the apparatus comprising of: a radiofrequency unit; and a processor, wherein the processor is configured toreceive a first physical control channel includes resource allocationinformation for resource block group (RBG), and to perform a process forreceiving a physical shared channel from one or more RBG is indicated bythe resource allocation information, wherein the one or more allocatedRBGs include an RB pair received the first physical control channel,wherein the RB pair is excluded from the process for receiving aphysical shared channel when the second slot of the RB pair is set to asearching space for a second physical control channel.

Preferably, the searching space for the second physical control channelis set by radio resource control (RRC) signaling.

Preferably, the first and the second physical control channel have beeninterleaved by a plurality of resource blocks.

Preferably, the first physical channel is used to carry downlink grant,and the second physical channel is used to carry uplink grant.

Preferably, the first and the second physical control channel includeRelay Physical Downlink Control Channel (R-PDCCH), and the physicalshared channel includes Relay Physical Downlink Shared Channel(R-PDSCH).

According to embodiments of the present invention, resources for aphysical channel can be efficiently allocated in a wirelesscommunication system, preferably, in a relay system. In addition, adownlink signal can be efficiently processed.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included as a part of detaileddescription to provide a further understanding of the invention,illustrate embodiments of the invention and together with thedescription serve to explain the technical principle of the invention.

In the drawings:

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in a 3rd Generation Partnership Project (3GPP) system;

FIG. 2 illustrates the structure of a radio frame in a 3GPP system;

FIG. 3 illustrates a resource grid for a downlink slot;

FIG. 4 illustrates the structure of a downlink subframe;

FIG. 5 illustrates the structure of an uplink subframe used in a 3GPPsystem;

FIG. 6 illustrates mapping of Virtual Resource Blocks (VRBs) to PhysicalResource Blocks (PRBs);

FIGS. 7 to 9 illustrate type 0 Resource Allocation (RA), type 1 RA, andtype 2 RA, respectively;

FIG. 10 illustrates a wireless communication system including relays;

FIG. 11 illustrates exemplary backhaul transmission using a MulticastBroadcast Single Frequency Network (MBSFN) subframe;

FIG. 12 illustrates a process of allocating resources for an R-PDCCH andreceiving the R-PDCCH using the allocated resources according to anembodiment of the present invention;

FIG. 13 illustrates exemplary R-PDCCH interleaving;

FIGS. 14 to 18 illustrate multiplexing methods of R-PDCCHs/R-PDSCHs inresources allocated by a DVRB scheme according to an embodiment of thepresent invention;

FIG. 19 illustrates exemplary R-PDCCH/R-PDSCH transmission;

FIGS. 20 and 21 illustrate exemplary R-PDCCH RB configuration;

FIGS. 22 to 24 illustrate exemplary R-PDCCH transmission according towhether interleaving is applied and blind decoding processescorresponding thereto;

FIG. 25 illustrates a process of mapping R-PDCCHs to PRBs;

FIG. 26 illustrates exemplary R-PDCCH/R-PDSCH RA;

FIG. 27 illustrates R-PDCCH mapping when interleaving is off;

FIG. 28 illustrates an example of configuring different SS RBs ordifferent SS RBGs over time;

FIGS. 29 to 32 illustrate exemplary R-PDCCH SS configurations accordingto RA types;

FIGS. 33 to 35 illustrate various examples of R-PDCCH SS configurationin RBGs;

FIG. 36 illustrates exemplary R-PDCCH DSS/CSS configuration;

FIG. 37 illustrates exemplary R-PDCCH transmission according to systembandwidth;

FIGS. 38 to 42 illustrate mapping operations for R-PDCCH transmission;

FIGS. 43 to 45 illustrate a rule of mapping R-PDCCHs to PRBs;

FIG. 46 illustrates R-PDCCH SS configuration according to aggregationlevel;

FIG. 47 illustrates R-PDCCH SS configuration when available PRBS arelimited; and

FIG. 48 illustrates a BS, an RN, and a UE which are applicable to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Configurations, functions, and other features of the present inventionwill be readily understood by the embodiments of the present inventiondescribed below with reference to the attached drawings. The embodimentsof the present invention can be used for a variety of radio accesstechniques, for example, CDMA, FDMA, TDMA, OFDMA, SC-FDMA, and MC-FDMA.CDMA may be embodied through radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be embodiedthrough radio technology such as Global System for Mobile communications(GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be embodied through radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMax), IEEE 802-20, and Evolved UTRA(E-UTRA). UTRA is a part of the Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) which uses E-UTRA.LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE.

Although the following embodiments are described focusing on the case inwhich technical features of the present invention are applied to a 3GPPsystem, this is purely exemplary and the present invention is notlimited thereto.

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in an LTE system.

When a User Equipment (UE) is powered on or enters a new cell, the UEperforms initial cell search such as synchronization adjustment with aBase Station (BS) (S101). To this end, the UE may receive a PrimarySynchronization Channel (P-SCH) and a Secondary Synchronization Channel(S-SCH) from the BS to establish synchronization with the BS and acquireinformation such as a cell identity (ID). Thereafter, the UE may receivea physical broadcast channel from the BS to thus acquire broadcastinformation within the cell.

Upon completion of the initial cell search, the UE may receive aPhysical Downlink Control Channel (PDCCH) and receive a PhysicalDownlink Shared Channel (PDSCH) according to information included in thePDCCH to acquire more detailed system information (S102).

Meanwhile, if the UE initially accesses the BS or has no radio resourcesfor signal transmission, the UE may perform a random access procedurewith respect to the BS (steps S103 to S106). To this end, the UE maytransmit a specific sequence through a Physical Random Access Channel(PRACH) as a preamble (S103 and S105), and receive a response message tothe preamble through the PDCCH and the PDSCH corresponding to the PDCCH(S104 and S106). If the random access procedure is contention-based, theUE may additionally perform a contention resolution procedure.

The UE which has performed the above procedures may then receive aPDCCH/PDSCH (S107) and transmit a Physical Uplink Shared Channel(PUSCH)/Physical Uplink Control Channel (PUCCH) (S108) as a generaluplink/downlink (UL/DL) signal transmission procedure. Controlinformation that the UE transmits to the BS on UL or receives from theBS includes a DL/UL Acknowledgement/Negative Acknowledgement (ACK/NACK)signal, a Channel Quality Indicator (CQI), Scheduling Request (SR), aPrecoding Matrix Index (PMI), a Rank Indicator (RI), and the like. Inthe 3GPP LTE system, the UE may transmit the control information such asCQI/PMI/RI through the PUSCH and/or the PUCCH.

FIG. 2 illustrates the structure of a radio frame used in a 3GPP system.

Referring to FIG. 2, a radio frame has a length of 10 ms (307200 T_(s))and includes 10 equally-sized subframes. Each of the subframes has alength of 1 ms and includes two slots. Each of the slots has a length of0.5 ms (15360 T_(s)). Here, T_(s) denotes a sampling time and isrepresented as T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns). Eachslot includes a plurality of Orthogonal Frequency Division Multiplexing(OFDM) symbols in the time domain and includes a plurality of ResourceBlocks (RBs) in the frequency domain. In the LTE system, one RB includes12 subcarriers×7 (or 6) OFDM symbols. A Transmission Time Interval (TTI)which is a unit time for data transmission may be determined in units ofone or more subframes. The above-described structure of the radio frameis purely exemplary and various modifications may be made in the numberof subframes included in a radio frame, the number of slots, or thenumber of OFDM symbols.

FIG. 3 illustrates a resource grid for a DL slot.

Referring to FIG. 3, a DL slot includes 7(or 6) OFDM symbols in the timedomain and N^(DL) _(RB) RBs in the frequency domain. Since each RBincludes 12 subcarriers, the DL slot includes N^(DL) _(RB)×12subcarriers in the frequency domain. Although FIG. 3 illustrates thecase in which a DL slot includes 7 OFDM symbols and an RB includes 12subcarriers, the present invention is not limited thereto. For example,the number of OFDM symbols included in the DL slot may vary according tothe length of a Cyclic Prefix (CP). Each element on the resource grid isreferred to as a Resource Element (RE). An RE is a minimumtime/frequency resource defined in a physical channel and is indicatedby one OFDM symbol index and one subcarrier index. One RB includesN_(symb) ^(DL)×N_(sc) ^(RB) REs where N_(symb) ^(DL) denotes the numberof OFDM symbols included in a DL slot and N_(sc) ^(RB) denotes thenumber of subcarriers included in an RB. The number of RBs included in aDL slot, N^(DL) _(RB), is determined based on a DL transmissionbandwidth configured in a cell.

FIG. 4 illustrates the structure of a DL subframe used in a 3GPP system.

Referring to FIG. 4, a DL subframe includes plural (e.g. 12 or 14) OFDMsymbols. A plurality of OFDM symbols starting from a front portion ofthe subframe is used as a control region and the remaining OFDM symbolsare used as a data region. The size of the control region may beindependently determined according to each subframe. The control regionis used to transmit scheduling information and layer 1/layer 2(L1/L2)control information, whereas the data region is used to transmittraffic. Control channels include a Physical Control Format IndicatorChannel (PCFICH), a Physical Hybrid automatic repeat request IndicatorChannel (PHICH), and a Physical Downlink Control Channel (PDCCH). Atraffic channel includes a Physical Downlink Shared Channel (PDSCH).

The PDCCH informs each UE or UE group of information related to resourceallocation of a Paging Channel (PCH) and a Downlink-Shared Channel(DL-SCH), a UL scheduling grant, HARQ information, etc. The PCH and theDL-SCH are transmitted through the PDSCH. Accordingly, a BS and a UEgenerally transmit and receive, respectively, data through the PDSCH,except for specific control information or specific service data.Control information transmitted through the PDCCH is referred to asDownlink Control Information (DCI). The DCI indicates UL resourceallocation information, DL resource allocation information, and a ULtransmit power control command for certain UE groups. Table 1 shows DCIaccording to DCI formats.

TABLE 1 DCI format Description DCI format 0 Used for scheduling of PUSCHDCI format 1 Used for scheduling of one PDSCH codeword DCI format 1AUsed for compact scheduling of one codeword and random access procedureinitiated by PDCCH order DCI format 1B Used for compact scheduling ofone PDSCH codeword with precoding information DCI format 1C Used forvery compact scheduling of one PDSCH codeword DCI format 1D Used forcompact scheduling of one PDSCH codeword with precoding and power offsetinformation DCI format 2 Used for scheduling of PDSCH to UEs configuredin closed-loop spatial multiplexing mode DCI format 2A Used forscheduling of PDSCH to UEs configured in open- loop spatial multiplexingmode DCI format 3 Used for transmission of TPC commands for PUCCH andPUSCH with 2-bit power adjustments DCI format 3A Used for transmissionof TPC commands for PUCCH and PUSCH with 1-bit power adjustments

DCI format 0 indicates UL resource allocation information, DCI formats 1to 2 indicate DL resource allocation information, and DCI formats 3 and3A indicate UL Transmit Power Control (TPC) commands for UE groups. A BSdetermines a PDCCH format according to DCI to be transmitted to a UE andattaches Cyclic Redundancy Check (CRC) to control information. A uniqueidentifier (e.g. Radio Network Temporary Identifier (RNTI)) is masked tothe CRC according to the owner or usage of the PDCCH.

FIG. 5 illustrates the structure of a UL subframe used in a 3GPP system.

Referring to FIG. 5, a lms subframe 500, which is a basic unit for LTEUL transmission, includes two 0.5 ms slots. In a normal CP, each slotincludes 7 symbols 502 each corresponding to one SC-FDMA symbol. An RB503 is a resource allocation unit corresponding to 12 subcarriers in thefrequency domain and one slot in the time domain. An LTE UL subframe isbroadly divided into a data region 504 and a control region 505. Thedata region refers to communication resources used for transmitting datasuch as voice and packets to each UE and includes a PUSCH. The controlregion refers to communication resources used for transmitting a DLchannel quality report received from each UE, an ACK/NACK for a receivedDL signal, and a UL SR and includes a PUCCH. A Sounding Reference Signal(SRS) is transmitted on an SC-FDMA symbol, which is located at the lastportion in one subframe in the time domain, through a data transmissionband in the frequency domain. SRSs of multiple UEs transmitted on thelast SC-FDMA symbol in the same subframe are distinguishable accordingto frequency positions/sequences.

RB mapping will be described below. Physical Resource Blocks (PRBs) andVirtual Resource Blocks (VRBs) are defined. The PRBs are configured asillustrated in FIG. 3. That is, a PRB is defined as N_(symb) ^(DL)contiguous OFDM symbols in the time domain and N_(sc) ^(R) contiguoussubcarriers in the frequency domain. PRBs are numbered from 0 to N_(RB)^(DL)−1 in the frequency domain. The relationship between a PRB numbern_(PRB) and an RE (k, l) in a slot is given by Equation 1:

$\begin{matrix}{n_{PRB} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

where k denotes a subcarrier index and _(N) _(sc) ^(RB) denotes thenumber of subcarriers included in one RB.

The VRB is equal to the PRB in size. A Localized VRB (LVRB) of alocalized type and a Distributed VRB (DVRB) of a distributed type aredefined. Regardless of VRB type, a pair of RBs is allocated by a singleVRB number n _(VRB) throughout two slots of a subframe.

FIG. 6 illustrates a method of mapping VRBs to PRBs.

Referring to FIG. 6, since LVRBs are directly mapped to PRBs, a VRBnumber n_(VRB) corresponds identically to a PRB number n_(PRB)(n_(PRB)=n_(VRB)). VRBs are numbered from 0 to N_(VRB) ^(DL)−1 whereN_(VRB) ^(DL)=N_(RB) ^(DL). Meanwhile, DVRBs are mapped to PRBs afterinterleaving. More specifically, the DVRBs may be mapped as shown inTable 2. Table 2 lists RB gap values.

TABLE 2 Gap (N_(gap)) System BW 1^(st) gap 2^(nd) gap (N_(RB) ^(DL))(N_(gap,1)) (N_(gap,2))  6-10 ┌N_(RB) ^(DL)/2┐ N/A 11 4 N/A 12-19 8 N/A20-26 12 N/A 27-44 18 N/A 45-49 27 N/A 50-63 27 9 64-79 32 16  80-110 4816

N_(gap) denotes a frequency gap (e.g. in PRBs) when VRBs of the samenumber are mapped to PRBs in the first and second slots of a subframe.If 6≦N_(RB) ^(DL)≦49, only one gap value is defined (N_(gap)=N_(gap,1)).If 50≦N_(RB) ^(DL)≦110, two gap values N_(gap,1) and N_(gap,2) aredefined. N_(gap)=N_(gap,1) or N_(gap)=N_(gap,2) is signaled through DLscheduling. DVRBs are numbered from 0 to N_(VRB) ^(DL)−1. IfN_(gap)=N_(gap,1), then N_(VRB) ^(DL)=N_(VRBgap1) ^(DL)=2·min(N_(gap),N_(RB) ^(Dl)−N_(gap)), and if N_(gap)=N_(gap,2), the N_(VRB)^(Dl)=N_(VRBgap2) ^(DL)=└N_(RB) ^(DL)/2N_(gap)┘·2N_(gap) where min(A,B)denotes a smaller of A or B.

Consecutive Ñ_(VRB) ^(DL) VRB numbers form a VRB number interleavingunit. If N_(gap)=N_(gap,1), then Ñ_(VRB) ^(DL)=N_(VRB) ^(DL), and ifN_(gap)=N_(gap,2), then Ñ_(VRB) ^(DL)=2N_(gap). VRB number interleavingof each interleaving unit may be performed using 4 columns and N_(row)rows. N_(row)=┌Ñ_(VRB) ^(DL)/(4P)┐·P where P denotes the size of aResource Block Group (RBG). An RBG is defined as P consecutive RBs. AVRB number is recorded in a matrix row by row and read from the matrixcolumn by column. N_(null) nulls are inserted into the last rows of thesecond and fourth columns and N_(null)=4N_(row)−Ñ_(VRB) ^(DL). A nullvalue is disregarded during reading.

Hereinbelow, resource allocation defined in legacy LTE will be describedwith reference to the drawings. FIGS. 7, 8, and 9 illustrate controlinformation formats for type 0 Resource Allocation (RA), type 1 RA, andtype 2 RA, respectively, and examples of RA corresponding thereto.

A UE interprets an RA field based on a detected PDCCH DCI format. An RAfield within each PDCCH includes two parts of an RA header field andactual RB allocation information. PDCCH DCI formats 1, 2 and 2A for type0 and type 1 RA have the same format and are distinguished through aone-bit RA header field according to DL system band. More specifically,type 0 RA is indicated by 0 and type 1 RA is indicated by 1. PDCCH DCIformats 1, 2, and 2A are used for type 0 or type 1 RA, whereas PDCCH DCIformat 1A, 1B, 1C, and 1D are used for type 2 RA. A PDCCH DCI formathaving type 2 RA does not contain an RA header field.

Referring to FIG. 7, RB allocation information in type 0 RA includes abitmap indicating an RBG allocated to a UE. An RBG is a set ofconsecutive PRBs. An RBG size P depends on system bandwidth as shown inTable 3.

TABLE 3 System BW RBG size N_(RB) ^(DL) (P) ≦10 1 11-26 2 27-63 3 64-110 4

The total number N_(RBG) of RBGs in a DL system bandwidth having N_(RB)^(DL) PRBs is given by N_(RBG)=┌N_(RB) ^(DL)/P┐ and the size of └N_(RB)^(DL)/P┘ RBGs is P. If N_(RB) ^(DL) modP>0 , the size of one of RBGs isgiven by N_(RB) ^(DL)−P·└N_(RB) ^(DL)/P┘ where mod denotes a modulooperation, ┌ ┐ denotes the ceiling function, and └┘ denotes the flooringfunction. The size of a bitmap is N_(RBG) and each bit of the bitmapcorresponds to one RBG. The RBGs are indexed from 0 to N_(RBG)−1 inascending order of frequency. RBG 0 to RBG N_(RBG)−1 are mapped to bitsstarting from the Most Significant Bit (MSB) to the Least SignificantBit (LSB) of the bitmap.

Referring to FIG. 8, in type 1 RA, RB allocation information of sizeN_(RBG) indicates resources within an RBG subset to a scheduled UE on aPRB basis. An RBG subset p (0≦p<P) includes every P-th RBG starting fromRBG p . The RB allocation information includes three fields. The firstfield includes ┌log₂(P)┐ bits indicating an RBG subset selected fromamong P RBG subsets. The second field includes one bit indicating ashift of RA span within the subset. If a bit value is 1, this representsthat the shift is triggered and, otherwise, this represents that theshift is not triggered. The third field includes a bitmap, each bitthereof indicates one PRB within the selected RBG subset. A bitmap partused to indicate a PRB within the selected RBG subset is N_(RB) ^(TYPE1)in size and is defined as Equation 2:

N _(RB) ^(TYPE1) =┌N _(RB) _(DL) /P┐−┌log₂(P)┐−1   [Equation 2]

An addressable PRB number in the selected RBG subset starts from anoffset Δ_(shif) (p) for the smallest PRB number within the selected RBGsubset and may be mapped to the

MSB of the bitmap. The offset is expressed as the number of PRBs andapplied within the selected RBG subset. If a bit value in the secondfield for shift of an RA span is set to 0, the offset for the RBG p isgiven by Δ_(shift)(p)=0. Otherwise, the offset for the RBG subset p isgiven by Δ_(shift)(p)=N_(RB) ^(RGB subset)(p)−N_(RB) ^(TYPE1) whereN_(RB) ^(RBGsubset)(p) denotes the number of PRBs in the RBG subset pcalculated by Equation 3.

$\begin{matrix}{{N_{RB}^{{RBG}\mspace{11mu} {subset}}(p)} = \left\{ \begin{matrix}{{{\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor \cdot P} + P},} & {p < {\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor {mod}\mspace{14mu} p}} \\{{\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor \cdot P} +} & {p = {\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor {mod}\mspace{14mu} p}} \\{{{\left( {N_{RB}^{DL} - 1} \right){mod}\mspace{14mu} P} + 1},} & \; \\{{\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor \cdot P},} & {p > {\left\lfloor \frac{N_{RB}^{DL} - 1}{P^{2}} \right\rfloor {mod}\mspace{14mu} p}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Referring to FIG. 9, RB allocation information in type 2 RA indicates aset of LVRBs or DVRBs which are consecutively allocated to a scheduledUE. If RA is signaled using the PDCCH DCI format 1A, 1B, or 1D, a 1-bitflag indicates whether LVRBs or DVRBs are allocated (e.g. 0 for LVRBallocation and 1 for DVRB allocation). Meanwhile, RA is signaled usingthe PDCCH DCI format 1C, only the DVRBs are allocated. A type 2 RA fieldincludes a Resource Indication Value (RIV) corresponding to a start RB(RB_(start)) and a length. The length indicates the number of virtuallyconsecutively allocated RBs.

FIG. 10 illustrates a wireless communication system including relays. Arelay (or Relay Node (RN)) serves to expand a service area of a BS or isinstalled a shadow area to provide a smooth service. Referring to FIG.10, a wireless communication system includes a BS, relays, and UEs. A UEcommunicates with a BS or a relay. For convenience, a UE communicatingwith a BS is referred to as a macro UE and a UE communicating with arelay is referred to as a relay UE. A communication link between a BSand a macro UE is referred to as a macro access link and a communicationlink between a relay and a relay UE is referred to as a relay accesslink. A communication link between a BS and a relay is referred to as abackhaul link.

The relay may be divided into a layer 1 (L1) relay, a layer 2 (L2)relay, and a layer 3 (L3) relay according to which function is performedin multi-hop transmission. Brief features of each relay are as follows.The L1 relay usually functions as a repeater and simply amplifiessignals from the BS/UE to transmit the amplified signals to the UE/BS.Since decoding is not performed in the L1 relay, this relay has theadvantage of shortening transmission delay but has the disadvantage ofamplifying noise too because it cannot distinguish between signals andnoise. To compensate for such a shortcoming, an advanced repeater orsmart repeater having functions such as UL power control orself-interference cancellation may be used. The L2 relay may performoperation of decode-and-forward and transmit user plane traffic to L2.In this relay, although noise is not amplified, a delay increase occursdue to decoding. The L3 relay is referred to as self-backhauling and maytransmit IP packets to L3. The L3 relay includes a Radio ResourceControl (RRC) function to serve as a small BS.

The L1 and L2 relays may be explained as parts of a donor cell coveredby a BS. If a relay is a part of a donor cell, since the relay cannotcontrol the cell thereof and UEs of the corresponding cell, the relaycannot have a cell ID thereof but may have a relay ID instead. In thiscase, some functions of Radio Resource Management (RRM) are controlledby a BS of the donor cell and parts of the RRM may be positioned in therelay. The L3 relay can control a cell thereof. In this case, the L3relay may manage one or more cells and each cell managed by the L3 relaymay have a unique physical-layer cell ID. This relay may have the sameRRM mechanism as a BS. In terms of the UE, there is no differencebetween access to a cell managed by the L3 relay and access to a cellmanaged by a normal BS.

In addition, relays are divided as follows according to mobilitythereof:

-   -   Fixed RN: This is permanently fixed for use in a shadow area or        for cell coverage extension. It is possible for the fixed RN to        simply serve as a repeater.    -   Nomadic RN: This may be temporarily installed when the number of        users is abruptly increased. The nomadic RN is movable within a        building.    -   Mobile RN: This can be mounted in public transportation vehicles        such as buses or subways and mobility thereof should be        supported.

The following classifications may be made according to a link between arelay and a network.

-   -   In-band connection: A network-to-relay link and a network-to-UE        link within a donor cell share the same frequency band.    -   Out-band connection: A network-to-relay link and a network-to-UE        link within a donor cell share different frequency bands.

The following classifications may also be made according to whether a UErecognizes presence of a relay.

-   -   Transparent relay: a UE is not aware that communication with a        network is performed through the relay.    -   Non-transparent relay: A UE is aware that communication with a        network is performed through the relay.

FIG. 11 illustrates exemplary backhaul transmission using a MulticastBroadcast Single Frequency Network (MBSFN) subframe. In an in-band relaymode, a BS-to-relay link (i.e. a backhaul link) operates in the samefrequency band as a relay-to-UE link (i.e. a relay access link). When arelay transmits signals to a UE while receiving signals from a BS, orvice versa, since a transmitter and a receiver of the relay createmutual interference, concurrent transmission and reception may belimited. To solve this problem, the backhaul link and the relay accesslink are partitioned by a TDM scheme. In an LTE-A system, a backhaullink is established in a subframe signaled as an MBSFN subframe (fakeMBSFN method) in order to support a measurement operation of legacy LTEUEs present in a relay zone. If a certain subframe is signaled as anMBSFN subframe, since a UE receives only a control region of thesubframe, the relay may configure the backhaul link using a data regionof the subframe. Specifically, the MBSFN subframe is used for BS-relaytransmission (e.g. R-PDCCH and R-PDSCH), starting from the third OFDMsymbol of the MBSFN subframe.

Hereinafter, a method for allocating and managing resources for arelay-PDCCH (R-PDCCH) is proposed with reference to the drawingsaccording to an embodiment of the present invention.

An R-PDCCH carries DCI for a relay. For details of DCI, reference ismade to Table 1. For example, the R-PDCCH may carry DL schedulinginformation and UL scheduling information for the relay. DL data for therelay (e.g. backhaul data) is received through a relay-PDSCH (R-PDSCH).A communication process using the R-PDCCH/R-PDSCH is performed in thesame or similar manner to step 102 in FIG. 1. That is, the relayreceives an R-PDCCH and receives data/control information through anR-PDSCH indicated by the R-PDCCH. R-PDCCH transmission processing (e.g.channel coding, interleaving, multiplexing, etc.) may be performed inthe same manner as processing defined in legacy LTE within a allowablerange or in a simplified manner of processing defined in legacy LTE whennecessary. For example, R-PDCCH transmission processing may omit anunnecessary process from processing defined in legacy LTE inconsideration of relay properties.

The relay performs R-PDSCH demodulation etc. based on controlinformation which is obtained from the R-PDCCH. Accordingly, it is veryimportant to accurately acquire R-PDCCH information. A legacy LTE systemuses a scheme for pre-reserving a PDCCH candidate region (PDCCH searchspace) in a control region and transmitting a PDCCH of a specific UE toa partial region of the pre-reserved region. Accordingly, the UE obtainsa PDCCH thereof within the PDCCH search space through Blind Decoding(BD). Similarly, even in the case of the relay, a scheme fortransmitting an R-PDCCH throughout a part or all of the pre-reservedresources may be used.

FIG. 13 illustrates a process of allocating resources for an R-PDCCH andreceiving the R-PDCCH using the allocated resources according to anembodiment of the present invention.

Referring to FIG. 12, a BS transmits R-PDCCH RA information to RNs(S1210). The R-PDCCH RA information is used to pre-reserve an R-PDCCHresource area. Namely, through the R-PDCCH RA information of this step,the RNs identify, in advance, resource positions in which an R-PDCCH islikely to be transmitted (R-PDCCH search space configuration). Forconvenience, signaling for R-PDCCH resource reservation of step S1210 isreferred to as signal#1. Signal#1 may use higher-layer signaling (e.g.RRC signaling, MAC signaling, etc.), desirably, RRC signaling. Signal#1may be transmitted in a semi-static manner. Signal#1 may also performedcell-specifically, relay group-specifically, or relay-specifically.

The R-PDCCH search space refers to R-PDCCH resources (R-PDCCH resourcearea) that an RN should monitor for reception of the R-PDCCH assignedthereto. The R-PDCCH search space includes a relay-common (RN-common)search space and/or a relay-specific (RN-specific) search space. A basicunit of the R-PDCCH resources includes an RB (e.g. 12 consecutivesubcarriers * 7 (or 6) consecutive OFDM symbols), a Resource ElementGroup (REG) (e.g. 4 available subcarriers * one OFDM symbol), or aControl Channel Element (CCE) (e.g. plural (e.g. 9) REGs).

Some or all of R-PDCCH resources (R-PDCCH search space) pre-reserved bysignal#1 are later used for actual transmission of the R-PDCCH. In mostcases, only some of the reserved R-PDCCH resources are used for R-PDCCHtransmission. Meanwhile, an RN should share resources with a macro UE ina data region of a backhaul subframe (e.g. MBSFN subframe). Accordingly,it is desirable to maximize multiplexing efficiency within a frame byapplying a conventional LVRB/DVRB resource mapping scheme as identicallyas possible to an RN as well as to a macro UE. Accordingly, the presentinvention proposes that signal#1 be configured based on the samesignaling information as LTE RA signal configuration in order to reserveR-PDDCH resources (e.g. R-PDCCH RBs). Specifically, signal#1 mayindicate VRB mapping scheme/allocation information. For example,signal#1 may indicate various VRB mapping schemes/allocation informationshown with reference to FIGS. 6 to 9. Desirably, signal#1 includesinformation about consecutive VRBs (e.g. start point and length) similarto a DVRB allocation scheme (refer to FIG. 9). The number of R-PDCCH RBspre-reserved according to signal#1 is desirably, but is not limitedthereto, a multiple of 4. Advantages that can be obtained when thenumber of R-PDCCH RBs is a multiple of 4 will be described later. Agranularity for R-PDCCH RA includes one RB, an RBG, or a group of X RBs(e.g. a group 4 RBs) according to necessity of RB allocation increment.Desirably, the R-PDCCH resource allocation granularity is 4 RBs or amultiple of 4 RBs, which will be described later.

Meanwhile, in legacy LTE, VRB allocation information (e.g. DVRB RAmapping signaling information) is transmitted only to one LTE UE.However, according to an embodiment of the present invention, RAinformation (signal#1) configured identically/similarly to conventionalVRB allocation information (e.g. DVRB RA mapping signaling information)may be transmitted to plural (e.g. all) RNs and the RNs may recognizethe positions of R-PDCCH resources according to a conventional LTE RArule (e.g. DVRB interleaving rule) (RN (group) common signaling).Although not shown, signal#1 may be transmitted only to one relay in thesame manner as in legacy LTE (RN dedicated signaling).

If signal#1 is transmitted through higher-layer signaling (R-PDCCH), anRN is unable to recognize a resource area reserved for the R-PDCCHduring initial access. Accordingly, the RN may be configured in a formof decoding the R-PDCCH under the assumption of the R-PDCCH is presentin a specific RB index during initial access (UE mode). Next, the RN mayrecognize the resource area reserved for the R-PDCCH from signal#1received through higher-layer (e.g. RRC) signaling in a semi-staticmanner (RN mode). However, if the reserved R-PDCCH area is changed, theRN may not accurately know from when the reserved R-PDCCH region hasbeen changed. In this case, problems may occur in R-PDCCH decoding. Evenif there are no problems in R-PDCCH decoding, the RN may have to attemptdecoding to detect the R-PDCCH in many cases. To minimize such problems,the size of the reserved R-PDCCH area may be increased or decreased by abasic unit. Such information should be considered in determining thepositions and number of R-PDCCH RBs included in semi-static RRCsignaling. For example, the reserved R-PDCCH area may be increased ordecreased by a multiple of 4 RBs. In this case, the RN performs aprocess of searching an R-PDCCH in an increased or decreased R-PDCCHarea as well as in an existing R-PDCCH area in the vicinity of asubframe in which the reserved R-PDCCH area is changed (i.e. thesubframe or before or after the subframe) (e.g. after receiving RRCsignaling). By doing so, decoding complexity caused by arbitrary R-PDCCHRB configuration can be mitigated.

Meanwhile, if the RN can directly receive the PDCCH, signal#1 may betransmitted through DCI of the PDCCH unlike the illustrated example(e.g. in the case in which subframe boundaries are misaligned by a fewsymbols in the BS and RN so that the RN can directly receive the PDCCH).Then, the relay can determine a resource area reserved for the R-PDCCHin the unit of every subframe.

Referring back to FIG. 12, the BS transmits an R-PDCCH in a backhaulsubframe (S1220). The R-PDCCH may be transmitted in some or all of theR-PDCCH resources (e.g. M PBs) reserved by signal#1. In most cases, onlysome of M reserved R-PDCCH RBs are used for R-PDCCH transmission. DCI(e.g. DL grant (scheduling information) and UL grant (schedulinginformation)) mapped to R-PDCCH resources (e.g. RBs) may not becross-interleaved. At this time, only one R-PDCCH is transmitted in oneor more RBs. Further, the DCI mapped to the R-PDCCH resources may beintra-RB interleaved. The DCI mapped to the R-PDCCH resources may alsobe inter-RB interleaved (cross-interleaved). In this case, a pluralityof R-PDCCHs may be transmitted together in one or more RBs. Next, eachRN monitors the R-PDCCH resources (R-PDCCH resource area) reserved bysignal#1 of step S1210 in order to determine whether an R-PDCCH thereofis present. Monitoring the R-PDCCH resources includes blind decoding ofR-PDCCH candidates. Each UE performs, upon detecting an R-PDCCHallocated thereto, an operation according to the DCI of the R-PDCCH(e.g. DL reception or UL transmission).

On the other hand, an R-PDCCH having a DL grant is supposed to betransmitted in the first slot and an R-PDCCH having a UL grant issupposed to be transmitted in the second slot. Accordingly, if theR-PDCCH is present only in the first slot (DL grant R-PDCCH), since thesecond slot may be wasted, it is desirable that an R-PDCCH betransmitted in the second slot. In this regard, an R-PDSCH resource areaallocated to a specific RN may be overlapped with a resource areareserved for an R-PDCCH (e.g. a resource area reserved by RRCsignaling). Then, an RN (procedure) may be configured so as to obtain anR-PDSCH only in the second slot for an overlapped RB. To raise resourceutilization, an RN (procedure) may be configured such that an R-PDSCH isdemodulated in the second slot only for an RB carrying an R-PDCCH andthe R-PDSCH is also demodulated in the first slot for an RB that doesnot carry an R-PDCCH. This is a scheme which uses conventional LTE RAbut enables the RN to determine the presence of a first R-PDCCH area andto obtain an R-PDSCH in the remaining area. This will be describedagain.

The present invention proposes a method for allocating resources for anR-PDCCH transmitted by a BS to an RN and managing the allocatedresources (e.g. RA type 2). All RNs demodulate an R-PDSCH based oncontrol information obtained from an R-PDCCH. Accordingly, it is veryimportant to accurately obtain R-PDCCH information. In a legacy LTEsystem, a resource area for transmitting a PDCCH is pre-reserved and aPDCCH of a specific UE is transmitted to a part of the reserved resourcearea. The resource area reserved for PDCCH transmission is referred toas a Search Space (SS). A UE obtains a PDCCH thereof through blinddecoding within the SS. The present invention uses a scheme fortransmitting an R-PDCCH to a specific RN in some or all of M R-PDCCH RBspre-reserved for transmitting information needed for R-PDSCHdemodulation. Such reservation can be performed by RRC signaling.Information about reservation may be broadcast through a PBCH. AnR-PDCCH SS may be cell-specifically or relay-specifically configured.The R-PDCCH SS may be semi-statically changed through RRC signalingafter it is configured.

The whole area in which R-PDCCHs are likely to be positioned may bepredetermined or may be indicated by RRC signaling. An area carrying anactual R-PDCCH or a partial area including the R-PDCCH area (e.g.RN-specific SS≦whole region) may be indicated by higher-layer signaling(e.g. RRC signaling). In this case, information about a limited SStransmitted to an RN may be used for determining an interleaverparameter, e.g. an interleaver size, for the R-PDCCH. That is,interleaver attributes may be determined according to which informationis transmitted to the RN. Especially, the same information may betransmitted to a plurality of RNs (e.g. RNs belonging to the sameinterleaving group) and the RNs may be jointly interleaved in allocatedRBs. Moreover, interleaver attributes may be determined according to thenumber of allocated RBs. In addition, information related to the limitedSS may be used to restrict the number of joint interleaved RNs (i.e. thenumber of RNs belonging to the same interleaving group). The informationrelated to the limited SS may also be used to restrict the number ofmapped RBs after interleaving. That is, there is an advantage of usingan interleaver of a predetermined size by interleaving and transmittingonly the designated number of RNs to the restricted or designated RBs.For example, if it is supposed to allocate only two RNs to 4 RBs, onlyan interleaver suitable for 4 RBs may be designed. To increase adegree-of-freedom of interleaving, 8 RBs or 2 RBs rather than 4 RBs maybe allocated. However, since complexity in interleaver design may beincreased, it is desirable to permit interleaving only for a limitednumber of RBs. For example, 2 or 4 RBs may be interleaved for 4 or 8RBs. In this case, since only two types of interleaver size aresufficient, it is unnecessary to support all types/sizes of interleaversand thus interleaver implementation is simplified.

A process of performing R-PDCCH interleaving using two sizes ofinterleavers according to the above-described method is illustrated inFIG. 13. Although R-PDCCHs are interleaved and then mapped toconsecutive RBs in FIG. 13 by way of example, RBs to which theinterleaved R-PDCCHs are actually mapped may not be consecutive.

Methods for multiplexing R-PDCCHs/R-PDSCHs in resources allocated by aDVRB scheme are illustrated with reference to FIGS. 14 to 18. Forconvenience, the case in which an R-PDCCH is transmitted in the firstslot and an R-PDSCH is transmitted in the second slot is shown. However,this is exemplary and the R-PDCCH may be transmitted in units of slotsand may be transmitted in the first slot and/or second slot. In LTE-A,an R-PDCCH having a DL grant is transmitted in the first slot and anR-PDCCH having a UL grant is transmitted in the second slot. Here, an RBmay refer to a VRB or a PRB according to context unless otherwisementioned.

FIG. 14 illustrates a method for multiplexing R-PDCCHs/R-PDSCHs for 4RNs in 24 DVRBs. The 4 RNs may mean an RN group preset to use 24allocated R-PDCCH RBs. That is, the shown R-PDCCH RBs may be exclusivelyused by the RNs (RN group). According to the DVRB scheme, since slotbasis cyclic shift (DVRB slot hopping) is applied, it is not guaranteedthat one RN uses two slots of the same PRB. That is, an R-PDCCH (and anR-PDSCH) is not transmitted to an RN using two slots of the same PRB. Inthis case, when the R-PDCCH/R-PDSCH is demodulated using a DemodulationReference Signal (DM-RS), channel estimation performance may be degradedand thus demodulation performance may also be deteriorated. Whenconsidering a good channel environment, in most cases, in which theR-PDCCH is transmitted, it is desirable to allocate two slots of thesame PRB to the same RN (i.e. R-PDCCH (and R-PDSCH)). To this end, it isproposed not to apply cyclic shift between slots (i.e. (DVRB) slothopping). In addition, resources for an RN are allocated to the same VRBset in the first and second slots. Slot hopping-off may be applied toall DVRB resources allocated by signal#1 or may be applied only toresources carrying the R-PDCCH.

Furthermore, it is proposed that a basic VRB pairing unit for DVRBsduring RA to an RN be set to a multiple of 4 during RA (VRB#0 to 3,VRB#4 to 7, VRB#12 to 15, and VRB#16 to 19). Resources for an RN areallocated to the same VRB set in the first and second slots. Accordingto this proposal, even if DVRB slot hopping is applied, two slots of thesame PRB may be used by the same RN as shown. In other words, two slotsof the same PRB may be used for R-PDCCH (and R-PDSCH) transmission ofthe same RN during DVRB RA irrespective of application of slot hopping.

Accordingly, a basic RA unit for an RN may be 4. For example, in asituation in which a distributed allocation or localized allocation aremixed for backhaul resources, 4 RBs may be used as a basic RA unit foran RN. Then, a multiple of 4 RBs may be allocated to an RN. In thiscase, the number of bits used for an RA field may be decreased by an RBstep (e.g. step=4). Moreover, even though cyclic shift is applied to 4RBs (e.g. VRB#0 to VRB#4) in the second slot, the cyclic-shifted RBs arecontiguous to one of 4 RBs of the first slot as shown. Therefore, evenif slot hopping (i.e. DVRB cyclic shift) is off only for M RBs (e.g.R-PDCCCH SS) pre-reserved for R-PDCCH transmission, the M RBs do notintrude other RBs to which slot hopping is not applied. Meanwhile, inthe case of the last VRB index of a DVRB, a group may be formed in unitsof 2 RBs rather than in units of 4 RBs.

FIG. 15 illustrates another method for multiplexing R-PDCCHs/R-PDSCHs inresources allocated by the DVRB scheme. This method shows an example ofallocating resources in a DVRB resource area assumed in FIG. 14 to an RNthat does not belong to the RN group of FIG. 14. By doing so, resourcesallocated to the RN group can be efficiently utilized.

Referring back to FIG. 14, since an R-PDCCH for RN#4 is not interleavedin an R-PDCCH (RN#0/1/2/3) area, RN#4 is not present in the R-PDCCHregion. That is, RN#4 is an RN of another group. For convenience,RN#0/1/2/3 of FIG. 14 are called RN Group#1 and resources (resourcearea) of FIG. 14 are called resources (resource area) for RN Group#1. Inthis example, even though RN#4 is an RN of another RN group, resourcesfor RN#4 (e.g. resources for RN#4 R-PDCCH and/or R-PDSCH) may beallocated in the resources (resource area) for RN Group#1, therebyincreasing resource use efficiency, as illustrated in FIG. 15. In thiscase, information indicating that the resources (resource area) areallocated to another RN (RN group) should be additionally transmittedtogether with or separately from RA signaling information. In anembodiment, a signal indicating an RN or an RN group (a Group IndicationSignal (GIS)) may be used. That is, the GIS and a DVRB signal may beused to allocate resources. The GIS may be inserted into an RA field oradded to a separate field. If the GIS does not change often, the GIS maybe indicated by higher-layer signaling (e.g. RRC signaling or MACsignaling).

FIG. 16 illustrates still another method for multiplexingR-PDCCHs/R-PDSCHs in resources allocated by the DVRB scheme. This methodmaximizes resource use efficiency by modifying a conventional RA scheme.

As illustrated in FIG. 16, if RN#0 is paired with RN#1 to form 4 RBs, acommon DVRB signal (PRB#0/6/12/18=VRB#0/1/2/3) may be transmitted toRN#0 and RN#1 to notify them of the allocated resource area but it ispossible not follow LTE PDSCH DVRB mapping in the second slot. That is,a signal may be reconfigured so that the first and second slots of thesame RB index are used without slot-based shifting. According to aconventional DVRB mapping rule, RB#0 in the first slot is supposed to becyclically shifted to RB#12 in the second slot according to a gap value.However, when R-PDCCHs/R-PDSCHs are demodulated using DM-RSs, cyclicshift may degrade channel estimation performance and thus deterioratedemodulation performance.

Accordingly, a signal may be reconfigured such that an RN uses, in thesecond slot, the same RB as an RB of the first slot without shifting anRB in the second slot. For this operation, additional signaling may notbe needed. A conventional operation mode and a proposed operation modemay be configured together. For example, shifting-off (i.e. slothopping-off) is applicable only to RBs to which R-PDCCHs are actuallyallocated. Alternatively, shifting-off may be applied to all RBs of anR-PDCCH SS. For an R-PDSCH, shifting-off is applicable only whenresources carrying an R-PDCCH are overlapped with resources indicated bythe R-PDCCH. In addition, shifting-off may be applied only to RBs towhich R-PDSCHs are actually allocated. Shifting-off may also beapplicable to all RBs available to an RN in a backhaul subframe.

FIG. 17 illustrates another method for multiplexing R-PDCCHs/R-PDSCHs inresources allocated by the DVRB scheme.

Referring to FIG. 17, an R-PDCCH resource area is previously given andeach RN monitors an R-PDCCH candidate area (i.e. an R-PDCCH SS) todetect an R-PDCCH thereof. In this method, it is proposed thatdetermination as to who will use the second slot according to the indexof a Relay CCE (R-CCE) to which an R-PDCCH of RN#k (k=0, 1, 2, 3) isallocated be made. For example, this method may be performed based on anR-CCE-index-to-RB-index mapping rule. The R-CCE-index-to-RB-indexmapping rule is not restricted to a specific one. For instance, thesecond slot of an RB carrying an R-PDCCH may be mapped to an RNcorresponding to the R-PDCCH. Specifically, if an R-CCE for RN#0 R-PDCCHis mapped to RB#0, an R-CCE for RN#1 R-PDCCH is mapped to RB#6, an R-CCEfor RN#2 R-PDCCH is mapped to RB#12, and an R-CCE for RN#3 R-PDCCH ismapped to RB#18, then the second slots of RB#0, 6, 12, and 18 carryingthe R-PDCCH may be mapped to RN#0, 1, 2, and 3, respectively, as shown.Thus, R-PDSCHs and R-PDCCHs can be allocated as illustrated in FIG. 17.

According to the above description, it is possible to allocate theresources of the second slot of an RB carrying an R-PDCCH to an RN (e.g.for an R-PDSCH) without additional signaling (implicit signaling). Theremaining RBs carrying R-PDSCHs may be allocated to RNs by RA includedin R-PDCCHs. In this case, an RN may be configured so as to demodulatean R-PDSCH by distinguishing RBs actually carrying R-PDCCHs from RBsthat do not carry R-PDCCHs. For this purpose, a method may be consideredthrough which the first slots of all RBs (an R-PDCCH SS) reserved forR-PDCCHs are not used for R-PDSCH transmission (or R-PDSCHdemodulation). As another method, an RN may exclude only the first slotof an RB from which an R-PDCCH thereof (it may be restricted to anR-PDCCH for a DL grant) is detected from R-PDSCH transmission (orR-PDSCH demodulation). More specifically, when an RN detects at leastpart of a DL grant R-PDCCH in the first slot of a PRB, the RN mayexclude the first slot of the PRB from R-PDSCH demodulation. As stillanother method, an RB carrying an R-PDCCH may be explicitly indicated.

FIG. 18 illustrates an extension of FIG. 17. Therefore, it is assumedthat the second slot of an RB carrying an R-PDCCH is implicitly mappedto an RN corresponding to the R-PDCCH as in FIG. 17. In this case, ifthere are a small number of RBs to which R-PDCCHs are mapped due to asmall number of RNs, some RBs in the second slot may not be allocated,thereby wasting resources. This resource waste may be prevented byincreasing a CCE aggregation level when there is a small of number ofRNs.

Referring to FIG. 18, if only R-PDCCHs for two RNs are present in anR-PDCCH resource area (e.g. 4 RBs), R-PDCCHs of the two RNs may betransmitted over the 4 RBs by increasing an R-PDCCH R-CCE aggregationlevel. To this end, a CCE-to-RB mapping rule may be used. Although theCCE-to-RB mapping rule is not specifically limited, R-CCE index 0 may bemapped to RB index 0, R-CCE index 1 to RB index 6, R-CCE index 2 to RBindex 12, and R-CCE index 3 to RB index 18 by way of example. As assumedabove, if 4 R-CCEs are present in 4 RBs (i.e. one R-CCE per RB), R-CCEindexes 0 and 1 may be mapped to RN#0 and R-CCE indexes 2 and 3 may bemapped to RN#1 (a CCE aggregation level=2). Thus an R-PDSCH of an RN maybe implicitly allocated so as to include one or more R-PDCCHtransmission areas. In the case of FIG. 18, the second slots ofRB#0/RB#6 are implicitly allocated to RN#0 (an R-PDSCH), and the secondslots of RB#12/#18 are implicitly allocated to RN#1 (an R-PDSCH).

Additionally, a method is described for allocating and demodulatingR-PDSCHs without using an implicit mapping relationship between R-CCEindexes and RB indexes shown in FIGS. 17 and 18. A BS may be scheduledto include an R-PDCCH of an RN during R-PDSCH allocation. In this case,the RN may appropriately demodulate/decode the R-PDSCH depending on amethod for detecting whether an R-PDCCH is present in the first slot ofan allocated R-PDSCH RB. As a conservative method, since the RN is ableto determine the position of an RRC configured R-PDCCH resource which issemi-statically allocated for the R-PDCCH, the RN demodulates theR-PDSCH under the assumption that the R-PDSCH is not present in thefirst slot of an RB reserved for the R-PDCCH. In this case, the R-PDCCHis regarded as being transmitted even though it is not actuallytransmitted and thus resources are wasted without being used for R-PDSCHtransmission.

As another method, the RN considers that an R-PDCCH is present duringR-PDCCH decoding in the first slot of an RB carrying at least part of anR-PDCCH (e.g. a DL grant) transmitted thereto (as a result ofinterleaving) in a decoding/demodulation process. That is, the RNdetermines that the R-PDSCH is transmitted only in the second slot ofthe RB. The RN determines that the R-PDSCH is transmitted also in thefirst slots of other R-PDSCH scheduled RBs. Here, since each RN is notaware of which RBs R-PDCCHs of other RNs use, the RN is unable to knowthe resulting effects. However, this problem may be solved by imposingconstraint on a scheduler. Specifically, the scheduler may restrict anRN to which an R-PDSCH is allocated in the second slot of a specific RBto one of RNs to which a part of an R-PDCCH is transmitted in the firstslot of the specific RB. In addition, the scheduler may operate suchthat an R-PDCCH transmitted to another RN is not included in an R-PDSCHscheduled RB area other than an RB carrying a part of an R-PDCCH. Thisis a scheduler implementation issue. The RN has to know that thedecoding/demodulation process should be performed according to the abovedescription. Accordingly, associated functions should be contained inimplementing an RN (method), which should be clarified by any means.

FIG. 19 illustrates exemplary R-PDCCH/R-PDSCH transmission according tothe above-described methods. In this example, it is assumed that a totalof 18 RBs (or RBGs) is present and RBs (or RBGs) #0, #3, #5, #6, #8,#11, #14, and #17 out of the 18 RBs (or RBGs) are SSs. It is alsoassumed that R-PDCCHs are transmitted only in RBs (or RBGs) #0, 90 3, 05, #6, #8, and #11 in a specific subframe. For R-PDCCH reception, it isassumed that RN 1 and RN 2 decode RBs #0, #3, and #6, and RN 3 and RN 4decode RBs #5, #8, and #11. The number of RBs that an RN should searchmay be indicated by RN-specific signaling.

Referring to FIG. 19, RN 1 and RN 2 assume that R-PDCCHs thereof may bepresent in RBs (RBGs) #0, #3, and #6 in the first slot of the subframe.Based on this assumption, RN 1 and RN 2 may successfully decode R-PDSCHsin the second slot of the subframe and other RBs (RBGs). Further, if RN1 and RN 2 can also be aware of areas to which R-PDCCHs of RN 3 and RN 4can be transmitted, i.e. RBs (or RBGs) #5, #8, and #11, RN 1 and RN 2determine that R-PDCCHs may be present in the first slots of RBs (orRBGs) #5, #8, and #11 as well as in the first slots of RBs (or RBGs) #0,#3, and #6 in the subframe. Thus, a BS may allocate R-PDSCHs only to thesecond slots of the RBs (or RBGs) or leave the second slots of the RBs(or RBGs) empty. It may also be assumed that the other RBs (or RBGs)#10,90 12, #13, #14, #15, #16, and #17 can carry R-PDSCHs of RN 1 or RN2, starting from first slots thereof (when the R-PDSCHs are scheduled).

Therefore, if an R-PDSCH is allocated to a PRB other than PRBs carryingR-PDCCHs, the R-PDSCH may be transmitted, starting from the first slotof the allocated PRB. On the contrary, in a PRB pair carrying anR-PDCCH, an R-PDSCH is allocated to the second slot of the PRB pair.

In order for RN 1 and RN 2 to identify PRBs, first slots of which arenot available for R-PDSCH transmission, the BS may signal actual PRBscarrying R-PDCCHs of group#1 and group#2. In addition, the schedulershould cause RNs of group#1 not to allocate R-PDSCHs for the RNs ofgroup#1 to PRBs carrying R-PDCCHs of group#2 (first slots) and, instead,to transmit R-PDSCHs, starting from the first slot, in PRBs other thanPRBs carrying R-PDCCHs for the RNs of group#1 and group#2. A decodingprocess of an RN is based on this assumption. Accordingly, an RNperforms R-PDSCH decoding starting from the first slot, if an R-PDCCH isnot present. On the contrary, if a PRB pair carries an R-PDCCH, the RNdoes not attempt R-PDSCH decoding in the first slot of the PRB pair. Forthis operation, blind decoding may be used, instead of signaling. Tofacilitate blind decoding, a unit (e.g. the number of RBs) forattempting blind decoding may be limited. For instance, if the RN failsto detect an R-PDCCH even though blind decoding is performed in one(e.g. 25 RBs) of candidate units, it may attempt blind decoding in ablind decoding RB area of the next size (e.g. 50 RBs). If the RNsucceeds in blind decoding, it is assumed that an R-PDCCH exists in theRBs. In this case, although the RN does not know whether any R-PDCCHexists in the other RBs, it may assume that at least an R-PDCCH thereofis not present in the other RBs. In addition, the RN assumes that anR-PDSCH thereof is present in an RB or RBG indicated by RA information.Accordingly, the RN may perform R-PDSCH decoding, determining that anR-PDCCH may exist in the first slot of an R-PDCCH-detected SS.Meanwhile, if an RA bit (an RB or RBG allocation indicator) indicatesthe presence of data in an SS in which an R-PDCCH has not been detected,the RN performs demodulation, determining that the first slot of the RBor the RBG does not include an R-PDCCH. The BS should allocate data toan appropriate RB in consideration of this case. In another method, anR-PDSCH for RN 1 of group#1 may be transmitted to an R-PDCCH area ofgroup#2. It is a natural result on the part of RN 1 because RN 1 doesnot know the presence of group#2. However, since the BS can determinewhether the R-PDSCH of RN 1 is overlapped with the R-PDCCH area ofgroup#2, the BS may perform scheduling in such a manner that the R-PDSCHof RN 1 is not overlapped with R-PDCCHs of RN 3 and RN 4. Meanwhile, anRN determines whether an R-PDCCH is transmitted through blind decodingand performs R-PDSCH decoding according to the determination. In themean time, the BS may inform each RN of RBs carrying an R-PDCCH. Forexample, the BS may inform each RN of which RBs participate in R-PDCCHtransmission in first slots thereof among RBs carrying R-PDSCHs.However, since the number of RBs of which the BS should inform the RN ischanged, a signaling format used to indicate the RBs is correspondinglychanged.

SS Design based on Multi-Level Blind Decoding

FIGS. 20 and 21 illustrate exemplary R-PDCCH RB configuration.

Referring to FIGS. 20 and 21, RBs carrying an R-PDCCH to a specific RNmay be semi-statically designated by RRC signaling and the R-PDCCH mayactually be transmitted through a part of the designated RBs. An actualresource area carrying an R-PDCCH may be identical to or different froman RRC-configured area (an interleaving unit in most cases). In thelatter case, the actual resource area carrying the R-PDCCH may bedetermined by blind decoding. That is, M RBs are configured as acandidate R-PDCCH transmission set and the R-PDCCH is transmittedthrough a subset of N RBs (M>N). Basically, different subsets may bedesignated for RNs (one RN may be distributed across a plurality ofsubsets). An RN performs blind decoding on an aggregation level basiswithin the subset in order to receive an R-PDCCH. The problem is that,because one RN does not know the positions of R-PDCCHs for other RNs,the BS transmits data in the remaining area except all positions atwhich R-PDCCHs are likely to be transmitted in the above-describedcandidate set or transmits data on the assumption that specific areas ofRBs or RBGs performing RA are available or unavailable for datatransmission. Here, full interleaving or partial interleaving isapplicable. Full interleaving refers to interleaving R-PDCCHs of all RNsaccording to an interleaving unit and then mapping the interleavedR-PDCCHs to PRBs, whereas partial interleaving refers to interleavingonly R-PDCCHs of some RNs. On the part of an RN, if one R-PDCCHinterleaving area is to be monitored, the RN may determine fullinterleaving, and if a plurality of R-PDCCH interleaving areas isincluded in a monitoring set, the RN may determine partial interleaving.Therefore, the terms may have different meanings in terms of a BS and anRN.

However, it may often occur that, after interleaving, an R-PDCCH of aspecific RN is not mapped uniformly to an R-PDCCH RB set of a total band(e.g. a system band) or a partial band. That is, if an interleaver unitis 4 REs (e.g. an REG), an R-PDCCH having 36 REs (e.g. one CCE) may bemapped uniformly to 9 RBs (4 REs per RB). However, if the R-PDCCH shouldbe mapped to 9 or more RBs, some RBs of the R-PDCCH subset may notinclude even a part (e.g. 4 REs) of the R-PDCCH of the RN. In this case,the R-PDCCH area cannot be used to transmit an R-PDSCH even though itdoes not include the R-PDCCH, like an R-PDCCH RB. That is, none of theRNs of an RN group that are interleaved can use the RBs of an R-PDCCHsubset for R-PDSCH transmission.

To avoid such resource waste, it is proposed that the interleaving range(e.g. a band or RBs) of an RN group be the same as the amount ofresources (e.g. a band or RBs) that can be allocated or used for all RNsof the RN group after interleaving. Although the two sizes may not beperfectly equal, an unmatched band or RBs are desirably minimized. Forexample, if 4 R-PDCCHs each having one RB should be transmitted to 4RNs, the 4 R-PDCCHs may be mapped to 4 RBs after interleaving. In thiscase, 4 consecutive logical indexes may be assigned to the R-PDCCHs.Meanwhile, 4 PRB indexes apart from one another by a predeterminedinterval (e.g. an RBG size unit of 3 or 4 RBs) may be used. Here, thepredetermined interval is determined in consideration of an RBG. Thus,the R-PDCCH PRB indexes may be non-contiguously assigned (e.g. 0, 4, 8 .. . ). Then, the 4 R-PDCCHs are transmitted across 4 RBs. If 7 RNs areto transmit a total of 7 R-PDCCHs (one R-PDCCH per RN) but if the basicinterleaving unit is a multiple of 4 RBs, a total of 8 RBs may bereserved for the 7 R-PDCCHs. In this case, resources corresponding tothe REs of one RB may substantially be wasted. Nonetheless, the proposedmethod can remarkably reduce resource waste, compared to theafore-described method. Configuration of the basic interleaving unitsuch as 4 serves to reduce the number of blind decoding procedures, asdescribed later. Blind decoding may be performed through a method forblind-decoding 4 RBs and then blind-decoding the next 4 RBs that do notoverlap with the previous 4 RBs or a method for blind-decoding RBs #0 to#3 (4 RBs) and then blind-decoding RBs #0 to #8 (8 RBs).

It is assumed that 8 RNs transmit 8 R-PDCCHs each having a size of oneCCE (e.g. the size of available REs in the first slot of one PRB pair),each RN transmitting one R-PDCCH. Then, a total of 8 RBs is required andinterleaving is performed on an 8-RB basis. In this method, the BS doesnot inform the RNs of a (partial) interleaving band/depth. Instead, itis known to the BS and the RNs that the interleaving band/depth isdefined as a multiple of 4 RBs when a minimum interleaving unit is 4RBs. Under this setting, each RN performs blind decoding on 4 RBs thatare the minimum unit (first-step blind decoding). If no R-PDCCHs aredetected, the RN may double the interleaving band/depth and thus performblind decoding on 8 RBs (second-step blind decoding). If the RN succeedsin blind decoding for the interleaving band/depth, the RN completes theband/depth search. On the contrary, if the RN fails in blind decodingfor the interleaving band/depth, the RN proceeds to the next R-PDCCHaggregation level search step. In this way, R-PDCCHs are interleaved inunits of a minimum required amount of RB resources and mapped to PRBs.Then the RN performs blind decoding on R-PDCCH resources with contiguouslogical indexes within a basic blind decoding range B1 (e.g. 4 CCEs)after deinterleaving. If the RN fails in blind decoding, it performsblind decoding in an increased bandwidth, i.e. an increased blinddecoding range B2 (e.g. 8 CCEs). Thus, the RN can successfully decode anR-PDCCH. The blind decoding of the blind decoding ranges B1 and B2 isperformed to determine an interleaving depth rather than an aggregationlevel. The basic granularity B1 may be set to various values such as 1,2, 3, 4, . . . and the blind decoding range B2 may be given as amultiple of B1 or the sum of B1 and a predetermined value.

An interleaver row size may vary with the size of an R-PDCCH to betransmitted/interleaved. While it is desirable to keep an interleavercolumn size unchanged, it is possible to change the interleaver columnsize within a given number of columns sizes (8, 16, and 32). Theinterleaver column size may be indicated by higher-layer signaling.Since the granularity with which the interleaver band/depth is changedis greater than 1, as many interleavers as the number of RBs in a systemband are not required. For example, if an interleaving size granularityis 16 RBs in a 96-RB system, about 6 interleaver sizes may be designed.

To reduce the number of interleavers to be designed, the followingmethod may be considered. For example, if an interleaver size is 4 andR-PDCCHs are to be transmitted with a band/depth of 8 RBs, two 4-RBinterleavers may be concatenated. That is, since the R-PDCCH band is 8RBs, two 4-RB interleavers can be used. In this manner, a system can beimplemented only with a single interleaver. As stated before, it ispossible to change an interleaver row size, while fixing an interleavercolumn size, or vice versa.

Once again, it is an important feature that the actual transmissionband/depth (e.g. 7 RBs) of the R-PDCCH is determined according to thesize of R-PDCCHs to be transmitted. In this case, the BS selects thesmallest interleaving band/depth (e.g. B1×2=8 RBs) including 7 RBs andtransmits the R-PDCCHs using the selected interleaving band/depth.Meanwhile, an RN performs blind decoding by increasing an interleavingband/depth or its index, starting from a basic interleaving band/depth,until an R-PDCCH is finally detected. Another feature is that a variableinterleaver size is used. Alternatively, a basic interleaver size isdefined and interleavers each having the basic interleaver size areconcatenated, for interleaving.

FIG. 22 illustrates the case in which an interleaving depth is notapplied. Each box of FIG. 22 is a logical representation of a CCEresource in the first slot. A CCE may be defined as 9 REGs or availableREs in the first slot of a PRB pair. Referring to FIG. 22, an R-PDCCH ismapped to one or plural CCEs according to a CCE aggregation level.

FIG. 23 illustrates the case in which an interleaving depth is appliedaccording to the present invention. Referring to FIG. 23, an RN performsblind decoding to determine an interleaving depth. That is, the RNperforms blind decoding with respect to blind decoding ranges B1, B2,B4, and B8 sequentially until an R-PDCCH is detected. If the RN fails inblind decoding in the ranges B1, B2, B4, and B8, the RN repeats the sameoperation with respect to the next aggregation level. For convenience,assuming that the RN succeeds in blind decoding of an R-PDCCH in theblind decoding range B2, the RN performs R-PDSCH demodulation on theassumption that an R-PDCCH exists in all RBs of B2. That is, the RNperforms R-PDSCH demodulation under the assumption that no R-PDSCHexists in all slots of the blind decoding range B2 as well as the firstslot of an RB in which the R-PDCCH has been detected. On the other hand,the RN does not assume that an R-PDCCH is present in the other areaexcept for the blind decoding range B2. Therefore, the RN performsR-PDSCH demodulation in allocated RBs, assuming that RBs indicated bythe BS (the remaining area) do not have an R-PDCCH. Obviously, anR-PDCCH may exist in the remaining area. However, since an R-PDSCH isallocated to an RB that does not carry an R-PDCCH, the RN can accuratelydemodulate the R-PDSCH while maintaining the assumption for RN R-PDSCHdemodulation (i.e. the absence of an R-PDCCH in the first slot of theallocated RB).

FIG. 24 illustrates multi-level blind decoding.

Referring to FIG. 24, an RN performs blind decoding for interleavingdepth B1. If the RN fails to detect an R-PDCCH, the RN performs blinddecoding for interleaving depth B2. Similarly, the RN increases theinterleaving depth until it succeeds in blind decoding. Althoughinterleaving randomizes inter-cell interference, different blinddecoding start positions for cells may be used to additionally obtain aninterference mitigation effect. In FIG. 24, a blind decoding startposition and a blind decoding depth Bi (i=1, 2, 3, . . . ) for each cellare exemplary and various modifications thereof may be made. Forexample, there is no need to set the blind decoding start position foreach cell in units of B1. A start offset may be determined according toa degree of interference. In case of a 3-cell structure, the offset maybe set to a system band/3. While Bi values are shown in one directionfrom the start point, the range of Bi area may be extended in bothdirections from a start index. Especially, when interleaving is notperformed, such an offset should be set to minimize interference. If thesame start index is set for each cell, an offset may be applied to aninterleaver for each cell. That is, an interleaver offset may be setaccording to a cell ID or a cell-specific value so as to achieve adifferent interleaving result for each cell.

Change of an interleaver size means change of a value of row x columnwhen necessary. If the number of columns is fixed, the number of rowsmay be changed or vice versa. The interleaver size may be changedaccording to the total number of REGs in a PRB to which an R-PDCCH ismapped. For example, assuming that one RB includes 8 REGs in the firstslot and a total frequency band is 20 MHz (i.e. 100 RBs), there are 800REGs (=8 REGs×100 RBs). Typically, all of the REGs are not defined as anSS. In this case, interleaved REG indexes are obtained by inputting 800REG indexes to a 32-column interleaver on a row basis, performing columnpermutation, and reading the permuted REG indexes column by column. Ifthe number of REGs for an SS is reduced to 400, interleaving may beperformed by reducing the number of rows, while the number of columns ismaintained. In this sense, the interleaver may be referred to as avariable interleaver.

Meanwhile, if a UL grant SS is configured independently in the secondslot of the subframe, the above-described proposed method may also beapplied to the second slot.

FIG. 25 illustrates an example of mapping R-PDCCHs to PRBs. Morespecifically, FIG. 25 illustrates a process for mapping logical R-PDCCHindexes (e.g. CCE indexes, REG indexes, or interleaving unit indexes) toPRBs through an interleaver. Interleaving may be performed only whenneeded. R-PDCCH-to-PRB mapping has the following features.

Interleaver size (the following attributes are applicable to everyafore-described interleaver)

Only the column size is fixed, while the row size is variable.

Or the column size may be fixed at a few values.

The column size may be fixed according to bandwidth.

Column permutation may be performed.

Interleaver On/Off

Whether to use the interleaver is determined according to a transmissionmode/configuration.

The interleaver is basically an off state. The interleaver may be on oroff by higher-layer signaling.

The interleaver is off all the time when DM RSs are used. For CRSs, theinterleaver is on all the time.

R-PDCCHs are mapped to PRBs at predetermined positions in an SS reservedfor R-PDCCH transmission (i.e. an R-PDCCH SS). If interleaving is off,an R-PDCCH is mapped in units of a basic unit (e.g. a CCE) (in otherwords, an R-PDCCH unit). If interleaving is on, the R-PDCCH is mapped inunits of REGs (in other words, an interleaving unit) and arranged atpredetermined REG indexes. Therefore, if interleaving is on, one R-PDCCH(e.g. a DL grant) is distributed to a plurality of PRBs.

Referring to FIG. 25, DL grant interleaving/mapping and UL grantinterleaving/mapping may be independently performed. For example, a DLgrant may be mapped to the first slot of a PRB pair, while a UL grantmay be mapped to the second slot of the PRB pair. In FIG. 25, while DLgrants are transmitted to RN 1, RN 2 and RN 3, UL grants may betransmitted only to RN 1 and RN 2. In this case, the DL grants areinterleaved and mapped to a plurality of PRBs, and the UL grants arealso interleaved and mapped to a plurality of PRBs. As illustrated inFIG. 25, an R-PDCCH SS is desirably configured in PRB pairs irrespectiveof interleaving on/off. That is, it is desirable to identicallyconfigure an RB set for DL grants (simply, DL grant SS or DL SS) and anRB set for UL grants (i.e. UL grant SS or UL SS), irrespective ofinterleaving on/off.

Meanwhile, when a DL grant is present in the first slot of a PRB pair,it may be necessary to indicate the use state of the second slot of thePRB pair (e.g. a UL grant, an (R-) PDSCH, empty, etc.). To this end,when a DL grant is positioned in the first slot of a PRB pair, an RA bitis used to indicate whether an R-PDSCH is present in the second slot ofthe PRB pair. In this case, it is desirable that an R-PDCCH for only oneRN be positioned in one RBG. However, when interleaving is applied, theR-PDCCH is distributed to a plurality of PRBs, thereby making itdifficult to use an RA bit properly. Accordingly, even though only a ULgrant for one of interleaved RNs is transmitted, the BS should informthe interleaved RNs whether a UL grant is present in all RBs to whichinterleaved UL grants are mapped.

For example, even though the BS does not transmit a UL grant to RN3, itshould signal the state of the second slot to RN3 if a UL grant SS ispresent in a resource area allocated for an (R-)PDSCH of RN3, becausethe BS transmits jointly interleaved UL grants of RN 1 and RN 2 in thesecond slot. The use state of the second slot may be signaled byhigher-layer signaling (e.g. RRC signaling) or physical-layer signaling.Because the BS is aware of the presence or absence of an interleavedR-PDCCH in an RB or RBG allocated for the (R-)PDSCH of RN3, the BSrate-matches the (R-)PDSCH, in consideration of an area having anR-PDCCH. However, when RN 3 decodes the R-PDCCH area, it should know thepresence or absence of an R-PDCCH and thus the use state of the secondslot needs to be signaled to RN3. As another example, it is possible toalways empty all areas in which R-PDCCHs are interleaved in the secondslot, for system simplification. Specifically, RN3 may empty the secondslot of a DL SS on the assumption that the second slot of the DL SS is aUL SS or decode a downlink signal on the assumption that the second slotof the DL SS has no (R-)PDSCHs. The BS may perform scheduling based onthe above assumption.

Multiplexing of Backhaul DL Data

If R-PDCCHs are interleaved, DL/UL grants of a plurality of RNs areinterleaved. Thus, PRBs of an RBG carrying the DL grants need to becarefully allocated. In other words, collision between RN data (e.g.(R-)PDSCHs) should be considered for PRBs other than R-PDCCH PRB pairsand collision between data and UL grants should be considered for thesecond slots of the R-PDCCH PRB pairs.

First, the case where an RA bit for a specific RBG carrying a DL grantindicates 0 will be considered. In this case, it is preferred that theBS not use any of the remaining PRB(s) of the specific RBG in order toavoid collision between data transmitted to RNs. Although it is possibleto allocate the PRB pairs of the RBG to another RN, each RN sharing theinterleaved DL grant cannot determine whether the PRB pairs are used forother RNs.

Next, the case where an RA bit for a specific RBG carrying a DL grantindicates 1 will be considered. In this case, an RN expects that datatransmission is performed in the RBG. The second slot of an R-PDCCH PRBpair may have two usages depending on whether the second slot isdesignated as a UL grant SS. If the second slot of a PRB pair carrying aDL grant in the first slot is designated as a UL grant SS byhigher-layer signaling, data transmitted in the second slot of the PRBpair may be subjected to strong interference caused by a UL grant foranother RN. That is, since an RN (RNs) is likely to receive a UL grantin the second slot of the R-PDCCH PRB pair, it is necessary not toallocate data for another RN to avoid collision between the data and theUL grant. On the other hand, if the second slot of the R-PDCCH PRB pairis not designated as a UL grant SS, data can be transmitted in thesecond slot of the R-PDCCH PRB pair.

Accordingly, the following RA methods may be considered. When an RA bitfor a specific RBG carrying a DL grant is 0, a PRB (PRBs) other than aPRB carrying the DL grant is not used for RN data transmission. On thecontrary, if an RA bit for an RBG carrying a DL grant is 1, anon-R-PDCCH PRB pair in the RBG is used for RN data transmission,whereas the second slot of an R-PDCCH PRB pair is not used for RN datatransmission. In another method, if an RA bit for an RBG carrying a DLgrant is 1 and the second slot of an R-PDCCH PRB pair is designated as aUL grant SS, the second slot of the R-PDCCH PRB pair is not used fordata transmission. In the other cases, the second slot of the R-PDCCHPRB pair is used for data transmission.

FIG. 26 illustrates the above proposed RA. This example is based on theassumption that DL grants for two RNs RN 1 and RN 2 are interleaved andallocated to R-PDCCH PRBs of at least two RBGs. For convenience, RA bitsfor first and second RBGs are assumed to be 0 and 1, respectively. InCase 1 of FIG. 26, the RBGs include at least part of a UL grant SS, andin Case 2, the RBGs do not include a UL grant SS. The rule of allocatingone RN per RBG and configuring an RBG in units of PRB pairs in an SS isalso applicable even when interleaving is used.

Upon detecting a DL grant in the first slot, an RN can identify an RB orRBG allocated thereto using the relationship between the CCE index of anR-PDCCH and a PRB. In this case, the RN can determine whether data ispresent in the second slot by interpreting an RB or RBG RA bitassociated with the PRB. For example, if CCEs are mapped to RBGs one toone or at the ratio of A:B, the RN may detect a CCE index and determinea PRB location thereof. Then, the RN can determine the presence orabsence of data in the second slot using an RA bit indicating the PRB.For instance, if a UL grant is present in the second slot, the RA bitmay indicate absence of data. The other PRB pairs except for the PRB inthe RBG may be used for R-PDSCH transmission.

FIG. 27 illustrates exemplary R-PDCCH mapping in the case whereinterleaving is off. When interleaving is off, an R-PDCCH for each RN ismapped on a CCE or slot basis without interleaving. If an R-PDCCHaggregation level increases, the number of PRBs for an R-PDCCH increaseswithin the same RBG. The aggregation levels of 2, 1 and 3 are set forRN1, RN2 and RN3, respectively in FIG. 27. If the aggregation levelexceeds the number of RBs designated as an SS, it may be extended toanother SS RBG. For instance, when one RB per RBG is designated as anSS, if the aggregation level is 4, the RN may obtain one R-PDCCH byperforming blind decoding over 4 RBGs.

During SS configuration, the first RB may be basically used as theR-PDCCH SS within a backhaul RBG allocated for an R-PDCCH SS. Sincedifferent backhaul resources may be allocated according to a channelstate over time, a change in an SS is indicated preferably by RRCsignaling. For example, if an RBG includes 4 RBs, an R-PDCCH SS may beconfigured with up to 4 RBs per RBG. If an RBG includes 3 RBs, anR-PDCCH SS may be configured with up to 3 RBs per RBG. However, if onlyCCE aggregation levels of 1 and 2 excluding 3 are supported, only twoRBs per RBG may be designated as part of an R-PDCCH SS. FIG. 27illustrates an example in which 4 RBs of an RBG are all designated asR-PDCCH transmission candidates on the assumption that each RBG includes4 RBs and a CCE aggregation level of 4 is supported. In FIG. 27, RN2performs blind decoding in a designated R-PDCCH SS (RBG2/3/5) anddetects a DL grant from the first PRB of RBG2 (PRB#4).

In fact, every RBG used as backhaul resources may correspond to an SS.Accordingly, RBGs designated as a backhaul resource area may benaturally designated as an SS. Alternatively, only some RBGs of thebackhaul resources may be designated as an SS. Depending on an exampleof implementation, frequency resources (e.g. RBGs) may be allocated toan SS in various manners. For instance, if the indexes of resourcesallocated for backhaul transmission are uniformly distributed in orderof odd numbers and even numbers, an SS may be configured withodd-numbered or even-numbered backhaul resources. It is also possible toconfigure an SS with every N-th frequency resource having apredetermined start offset.

SS Configuration Patterns and Signaling

FIG. 28 illustrates an example of configuring different SS RBs ordifferent SS RBGs over time. Since the frequency positions of backhaulresources may change over time to obtain a frequency-selectivescheduling gain, different SS RBs or different SS RBGs may beconfigured. An SS may always be configured in units of a PRB pair. Inthis case, the same mapping area may be set for an interleaved ornon-interleaved R-PDCCH (e.g. a DL grant) in the first slot and aninterleaved or non-interleaved R-PDCCH (e.g. a UL grant) in the secondslot. That is, a DL grant SS and a UL grant SS may be identical.Preferably, the DL grant SS and the UL grant SS may be identical only ina non-interleaving mode. In addition, the UL grant mapping area of thesecond slot may be equal to or smaller than the DL grant mapping area ofthe first slot. In other words, the UL grant mapping area may be asubset of the DL grant mapping area.

Referring to FIG. 28, a reference SS configuration is shown at theleftmost side. The reference SS configuration is arbitrarily definedbasic SS configuration for the purpose of description. Depending onimplementation, the reference SS configuration may not be definedseparately. In this example, an SS may change over time,cell-specifically, RN group-specifically, or RN-specifically. As shown,when an SS configuration set includes SSs Conf#1, Conf#2, and Conf#3,one of the SSs may be transmitted to change SS configuration. The SSconfiguration may be changed semi-statically by higher-layer signaling(e.g. RRC signaling) or dynamically by physical-layer signaling.

If an SS is limited to one PRB (pair) per RBG, the PRB (pair) for an SSmay be at various positions in an RBG. However, considering RS-baseddemodulation, the middle RB of an RBG is preferable for the SS toachieve better performance. For example, if an RBG includes 3 RBs, thesecond RB may be used for the SS. Similarly, if an RBG includes 4 RBs,the second or third RB may be used for the SS. In this case, althoughthe SS may be fixed to the second or third RB, an RB used as the SS isdesirably signaled so as to be changed according to environment. An RBused for an SS may be changed semi-statically by higher-layer signaling(e.g. RRC signaling) or dynamically by physical layer signaling.

Other examples of signaling for SS configuration are as follows.

1. Signaling of DM RS-based demodulation or CRS-based demodulation.

2. Signaling of interleaving mode or non-interleaving mode.

3. Signaling of the position of an SS RB in an RBG: e.g. for case of 4RBs→1, 2, 3, and 4 (four positions).

4. Signaling a relay backhaul resource area or a boundary: e.g. one ofcandidate boundaries is signaled.

While the above signals may be transmitted separately, they may betransmitted together in specific fields of the same RRC signal.

SS Configurations based on RA Type

An R-PDCCH SS may be configured according to an RA type as follows. Asdescribed before with reference to FIGS. 7 to 9, RA Types 0, 1 and 2 aredefined in legacy LTE. A description will first be given of RA Type 2.

FIGS. 29 and 30 illustrate examples of configuring an R-PDCCH SS usingRA Type 2. In FIGS. 29 and 30, DVRBs are illustrated. Referring to FIGS.29 and 30, the concept of an RBG subset may be introduced to RA Type 2,for SS configuration, like RA Type 1 of legacy LTE. An R-PDCCH SS may beconfigured within the same RBG subset from among resources allocated byRA Type 2. For example, if PRB indexes #0, #1, #2, 0 3, 0 16, #17, #18,and #19 constitute subset #0, an SS is configured preferably within thearea of subset #0. Likewise, if PRB indexes #4, #5, #6, #7, #20, #21,#22, and #23 constitute subset #1, an SS is configured preferably withinthe area of subset #1.

FIG. 31 illustrates an example of configuring an R-PDCCH SS according toRA Type 0. Referring to FIG. 31, only the concept of an RBG is used butthe concept of an RBG subset is not explicitly defined, in RA Type 0.Nonetheless, for SS configuration, a BS/RN may regard RBGs #0, #3, #6,and #9 as subset #0, RBGs #1, 0 4, #7, and #10 as subset #1, and RBGs#2, #5, and #8 as subset #2. As described before, it is desirable toconfigure an R-PDCCH SS within the same subset Therefore, the R-PDCCH SSmay be defined in, for example, subset #0. If there are many R-PDCCHs,the R-PDCCH SS may be defined in subset #0 and subset #1. If moreR-PDCCHs exist, the R-PDCCH SS may be defined in every subset. In mostcases, one subset #k (k=0 to p) may be sufficient for the R-PDCCH SS.

FIG. 32 illustrates an example of configuring an R-PDCCH SS according toRA Type 1. Referring to FIG. 32, RA Type 1 is a typical example to whichthe concept of an RBG subset (shortly, a subset) is introduced. Asillustrated, in the case of a system band of 32 RBs, three subsets maybe configured. The R-PDCCH SS is desirably configured using RBGs of thesame subset index, first of all. In FIG. 32, subset #0 includes RBGs#0/#3/#6/#9. Hence, the R-PDCCH SS may be configured using RBGs#0/#3/#6/#9. Whether all or part of the RBGs of subset #0 are used isindicated by separate signaling or determined according to a presetpattern. It is also preferred to create a bitmap indicating a specificsubset and specific RBGs within the specific subset. For example, thebitmap may be created to indicate subset=0 and RBGs=0 and 6. In the caseof 32 RBs, a 6-bit signal, including a subset indicator of 2 bits and anRBG bitmap indicator of 4 bits, is sufficient. This indicationinformation may be semi-statically transmitted by RRC signaling. If asingle subset is used to configure the R-PDCCH SS, the subset is fixedas a specific subset (e.g. subset #0) and only an RGB bitmap indicatormay be signaled. If one or more subsets are used to configure theR-PDCCH SS, these subsets may be indicated by a bitmap. When the size ofthe bitmap is large, the subset indication information may be reduced bycompression, for example, by representing a start subset and a subsetlength.

If the R-PDCCH SS is designated within a single subset in abovedescription, it is proposed that SS RBs be spaced apart from one anotherby the square of P wherein P is the number of RBs in an RBG. In theabove example of 32 RBs, 11 RBGs may be defined. Since each RBG includes3 RBs, P=3. Accordingly, the R-PDCCH SS RBs may be disposed with aspacing of 9 RBs (=3²). If a plurality of subsets is used for the SS, P²is the interval between SS RBs in each subset. The interval betweensubsets may be determined according to selected subsets and the numberof the selected subsets.

Meanwhile, in legacy LTE, the start position of an SS is different foreach aggregation level. However, there is no need to differentiate thestart position of an SS for an RN on a backhaul link according to anaggregation level. In this case, depending on a DCI payload size and asubblock interleaver size, the aggregation level of specific DCI may notbe determined and as a result, a PUCCH resource assignment generatedbased on CCE-to-ACK/NACK linkage may not be detected correctly. However,setting of a different start position for an SS according to eachaggregation level causes difficulty in actual PRB mapping. While a PDCCHSS is mapped to contiguous PRBs in a control region, an R-PDCCH SS ispresent in non-contiguous PRBs and is subject to the constraint that aDL grant and a UL grant exist in the same PRB pair. Therefore, it isdesirable to keep the start position of blind decoding for aggregationlevel N (e.g. 1) and the start position of blind decoding foraggregation level M (e.g. 2) equal. Then the burden of calculating ahash function in order to determine the start position of blind decodingfor each aggregation level is reduced.

A method for implicitly matching the blind decoding start positions of aDL grant and a UL grant (or it may be assumed that they are identical)is proposed. That is, if the total number of CCEs of an R-PDCCH SS for aDL grant is N, the total number of CCEs of an R-PDCCH SS for a UL grantmay be maintained at N. In this case, the index of the start position ofthe DL grant (e.g. a start CCE index for DL grant blind decoding)obtained using the hash function may be reused as the index of the startposition of the UL grant (e.g. a start CCE index for UL grant blinddecoding) for the same RN. In this case, there is no need to calculatethe hash function for the UL grant.

If an SS is configured using one RB in an RBG, the RB is preferablypositioned in the middle of an RBG. To simplify implementation, it isalso possible to set only one PRB located at one end of an RBG as an SS.However, if SS resources are allocated on an RBG basis, since all RBs ofan allocated RBG configure an SS, any RB of the RBG may be used for theSS.

If an RBG includes fewer RBs than P, an SS may be configured only with apredetermined number of RBs (N: N<P) in an RBG. For example, the SS maybe configured with N RBs counted from the first RB of each RBG or with NRBs counted from the last RB of each RBG.

Considering a shift in a subset in RA Type 1, it may occur that, eventhough a subset includes Q RBGs, all of the Q RBGs cannot be signaled toan RN in association with RA. Therefore, the scheduler preferably mapsan R-PDCCH in consideration of this case. In FIG. 32, in the case ofsubset#0 and shift#0, an RA bitmap indicates only RBGs#0, #3, and #6 outof RBGs#0, #3, #6, and #9. Hence, all of the RBGs need not beblind-detected on the part of an RN. Thus, three RBGs may be determinedto be a maximum blind decoding size in the above example. The maximumblind decoding size may vary with bandwidth. For instance, if 96 RBs areused, P=4 and a total of 25 RBGs is defined and RA is indicated onlywith respect to part of the 25 RBGs.

FIGS. 33 to 35 illustrate various examples of configuring an R-PDCCH SSin RBGs according to the above-described methods. In FIGS. 33 to 35, anR-PDCCH SS is configured using RBGs within the same RBG set.Specifically, FIG. 33 illustrates an example of configuring an SS usingthe middle RB pair of each RBG in an RBG subset when an RGB includes 3RBs. In FIG. 34, two SSs are configured in different RBG subsets. InFIG. 34, when the last RBG includes fewer RBs than P, an SS may beconfigured only with a predetermined number of RBs (e.g. 2 RBs) in theRBG. FIG. 35 illustrates an example of configuring an SS using all RBpairs in each RBG.

Common Search Space

At least in a CRS-based R-PDCCH demodulation mode, a DL grant CommonSearch Space (CSS) and/or a UL grant CSS may be configured. Preferably,a CSS may be set only for UL grants. If both DL and UL grants areinterleaved and a smaller number of UL grants is paired with DL grants,only the smaller number of UL grants may be filled in PRB pairs throughinterleaving, while the other areas of the PRB pairs may not be used.This problem may be solved via the following methods.

One of the methods is that, in the case of partial (or full)interleaving, the second slots of PRB pairs (in an interleaving group)are not used for R-PDSCH transmission even though only one UL grant isinterleaved in the second slots of the PRB pairs. Unused REGs of thesecond slots may be used by indicating distributed positions of REGs ofthe (interleaved) UL grant through signaling. Alternatively, the secondslots of the PRB pairs may always be left empty irrespective oftransmission of the (interleaved) UL grant. In this method, an R-PDSCHis rate-matched in consideration of a distributively positioned UL grantfragment.

As another method, when a DL grant SS and a UL grant SS areindependently configured and significant resource waste is expected dueto a relatively small number of UL grants with respect to DL grantsirrespective of the positions of the DL grants, the UL grants may bedisposed in a CSS. According to this method, the second slots of PRBpairs carrying a plurality of DL grants can be used for another purpose(e.g. R-PDSCH transmission), thereby reducing resource waste. Meanwhile,some UL grants may be paired with DL grants and thus the paired UL andDL grants may be positioned in the same PRB pairs. Therefore, an RNfirst attempts to detect a DL grant in the first slot of an RB pair inorder to receive an R-PDCCH. Upon detection of the DL grant in the firstslot, the RN attempts to detect a UL grant in the second slot of the RBpair. If the RN fails to detect a UL grant in the RB pair, the RNattempts to detect a UL grant in a UL grant CSS configured in the secondslot.

A third method is to differentiate a DL grant interleaving size from aUL grant interleaving size. For instance, DL grants may be partiallyinterleaved in units of 4 RBs, whereas UL grants may be partiallyinterleaved in units of 2 RBs. To facilitate DL and UL grantinterleaving of different sizes, a DL grant resource area and a UL grantresource area should be independently managed. As stated before, when aUL grant CSS is used, interleaving of different sizes can be applied.

In FIG. 36, areas A and B denote a DL grant SS and a UL grant SS,respectively. The area A may be a Dedicated SS (DSS) and the area B maybe a CSS. Each of the areas A and B may be configured to have both a DSSand a CSS. An SS may be a DSS or a CSS according to types of RSs forR-PDCCH demodulation. For example, if DM RSs are used, a DSS may beconfigured. If CRSs are used, a CSS may be configured. It may beindicated by signaling whether an SS is a DSS or a CSS.

CCE Aggregation Levels based on RBG

RBG size depends on system Bandwidth (BW). In LTE, RBG sizes are definedas 1, 2, 3 and 4 RBs according to system BWs. If a system BW includes 64to 110 RBs to ensure compatibility with legacy LTE, each RBG includes 4RBs. Accordingly, the CCE aggregation levels of R-PDCCHs may be limitedto one or more sets of (1, 2, 3, 4), (1, 2, 3), (1, 2, 4), and (1, 2)(e.g. 1 CCE=1 RB). An example of R-PDCCH transmission in a system BW of64 to 100 RBs is illustrated in FIG. 37. If the BW includes 27 to 63RBs, the RBG size is 3 RBs and thus the CCE aggregation levels ofR-PDCCHs may be limited to one or more sets of (1, 2, 3), (1, 2), and(1, 3). If the BW includes 11 to 26 RBs, the RBG size is 2 RBs and thusthe CCE aggregation levels of R-PDCCHs may be limited to one or moresets of (1, 2), (1), and (2). It is possible to set the CCE aggregationlevel to 1, 2, 3 and 4 and then to limit the highest CCE aggregationlevel to one of the values, to cover all cases. For example, differentaggregation levels may be supported according to BWs.

Table 4 illustrates supportable aggregation levels for different BWs.

TABLE 4 System BW RB] Supportable aggregation level  64~110 1, 2, 3, 427~63 1, 2, 3 11~26 1, 2 <=10 1 or non-support

Interleaving and Mapping for R-PDCCH

FIG. 38 illustrates a mapping operation for R-PDCCH transmission. Thisexample is characterized in that an R-PDCCH is interleaved and mapped toa PDSCH area according to a VRB-to-PRB mapping rule in order to transmitthe R-PDCCH in the PDSCH area, instead of an LTE PDCCH area. For R-PDCCHtransmission, various interleaving schemes and various mapping schemescan be used. It is also possible to subject CCEs to interleaving(partial interleaving) on a group basis and then map the interleavedCCEs, based on the operation of FIG. 38. On the part of an RN, anoperation for detecting an R-PDCCH in one or more partial-interleavedareas may be included.

FIG. 38 is based on the assumption that an area in which an R-PDCCH(R-PDCCHs) corresponding to 8 CCEs (e.g. 1 CCE=8 REGs) can betransmitted is semi-statically signaled and the R-PDCCH is actuallytransmitted in resources corresponding to 6 CCEs (all or each of 6 CCEsmay be used by one RN). The size of a CCE may differ according to anormal CP or an extended CP or according to a CRS mode or a DM-RS mode.Herein, it is assumed that 8 REGs of a PRB in the first slot areavailable and defined as one CCE in case of a normal CP/DM-RS mode. InFIG. 38, a bandwidth includes 50 RBs and one PRB per RBG (1 RBG=3 RBs)is used for R-PDCCH transmission. The RBG size may be determined asdefined in legacy LTE.

Interleaving & Permutation

In Method 1, 8 CCEs including nulls are interleaved (including columnpermutation according to a column permutation pattern). Bit reversal isused as an example of the column permutation pattern. For reference, anRN-specific SS (within a logical CCE index domain) is assumed. Method 2will be described later. Method 3 is different from Method 1 in that oneor more interleaving units are used. For example, 8 CCEs are dividedinto a plurality of parts (e.g. two parts each having 4 CCEs) andinterleaved in Method 3. Meanwhile, if RB-level permutation is performedduring VRB-to-PRB mapping (e.g. using bit reversal), REG-level columnpermutation or bit reversal may be omitted during interleaving, whichdoes not affect performance much. For reference, an SS in a logical CCEdomain is assumed to be a CSS (accessible to all RNs) in Method 3. Theuse of an RN-specific SS may slightly decrease operation efficiency orresource efficiency, but does not limit the application of the presentinvention.

After interleaving and permutation, an R-PDCCH is mapped to PRBsaccording to various rules. To describe the mapping, the concept of aVRB may be used. In the example of FIG. 38, 8 REGs, namely, 1, 33, 17,N, 9, 41, 25, N (where N is a null REG) among values (outputs) readcolumn-wise after interleaving and permutation constitute one VRB. Whilea VRB and a CCE are equal in size in FIG. 38, it is determined that thesame performance may be achieved even though the VRB size is larger thanthe CCE size. Even in case of a normal CP, the following various numbersof REGs are available. Therefore, the CCE size and the VRB size may bechanged based on the number of available REGs per RB according to atransmission mode, as follows.

1^(st) slot:

-   -   8 REGs in the 1^(st) slot (e.g. DM RS used)    -   11 REGs in the 1^(st) slot (e.g. CRS used)

2^(nd) slot:

-   -   15 REGs in the 2^(nd) slot (e.g. DM RS used and 4TX CRS)    -   16 REGs in the 2^(nd) slot (e.g. DM RS used and 2TX CRS)    -   18 REGs in the 2^(nd) slot (e.g. CRS used and 4TX CRS)    -   19 REGs in the 2^(nd) slot (e.g. CRS used and 2TX CRS)

For example, when a DL grant is transmitted in the first slot, the DLgrant is interleaved by defining one CCE as 8 REGs. A VRB size may bedefined as 8 REGs in case of DM RSs and as 11 REGs in case of CRSs.According to this method, a detection operation may be facilitated byfixing the CCE size. In addition, the VRB size is defined as an optimumvalue (e.g. the number of available REGs) to efficiently use the numberof available REGs which varies according to an RS mode. Therefore,resource waste can be minimized.

It is also desirable in the second slot to define one CCE as 8 REGs andone VRB as 15, 16, 17, or 19 REGs in actual VRB-to-PRB mapping. The sizeof one VRB is given as an example according to a change in RSs and TXantennas. The VRB size may be changed even if the same logic and ruleare used.

VRB-to-PRB Mapping

The simplest mapping rule is to sequentially map VRB indexes to R-PDCCHPRB indexes (renumbered indexes only for R-PDCCH RBs or indexes labeledin an R-PDCCH area in FIG. 38) at 1:1. Despite its simplicity, thismapping rule causes localization of jointly interleaved CCEs in a partof an R-PDCCH PRB (R-PDCCH PRBs). The localization may not matter if thepart includes 4 or more PRBs, while it may cause a problem withdiversity gain if the part includes PRBs less than 4 PRBs.

In another method, permutation may be performed (e.g. using bitreversal) at an RB level. This method is advantageous in that a rule issimple and VRBs are uniformly mapped to PRBs. For example, if a total offour R-PDCCH PRBs is present, VRB #0 (00), VRB #1(01), VRB #2(10), andVRB #3(11) may be mapped to R-PDCCH PRBs #0(00), #2(10), #1(01), and#3(11), respectively. If the number of R-PDCCH PRBs is not 2^(N), VRBsmay be mapped to the R-PDCCH PRBs by a method such as pruning, while thebit reversal rule is maintained. When bit reversal is applied, it ispreferable not to use column permutation (e.g. REG-level bit reversal)during interleaving. However, both REG-level bit reversal and RB-levelbit reversal may be applied only if implementation complexity permits.

In a further method, a rule that enables uniform distribution may beused. For example, a VRB index i may be mapped to a PRB index f(i) asindicated by Equation 4. In Equation 4, N represents the size of aphysical R-PDCCH area (e.g. a PRB unit) and K represents the size of anactual R-PDCCH to be transmitted (e.g. a PRB unit). Even when numbers ofavailable REs in a VRB and a PRB differ, K is calculated in terms ofPRBs. Herein, a, b and c are constants.

$\begin{matrix}{{f(i)} = {{c*\left\lfloor \frac{{i*N} + a}{K} \right\rfloor} + b}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Table 5 and Table 6 illustrate VRB-to-PRB mapping according toEquation 1. Table 5 illustrates VRB-to-PRB mapping when K=7, N=16,a=b=0, and c=1. That is, Table 5 illustrates mapping of VRB indexes 0 to7 (8 RBs, K=7) to R-PDCCH PRB indexes 0 to 16 (17 RBs, N=16). Table 6illustrates VRB-to-PRB mapping when K=7 and N=24.

TABLE 5 VRB index 0 1 2 3 4 5 6 7 PRB index (R- 0 2 4 6 9 11 13 16PDCCH)

TABLE 6 VRB index 0 1 2 3 4 5 6 7 PRB index (R- 0 3 6 10 13 17 20 24PDCCH)

A mapping pattern may be shifted or a mapping interval is adjusted usingthe additional parameters a, b, and c in Equation 4.

While REG-to-PRB mapping is not described in detail in FIG. 38, it maybe carried out in various manners. For example, REGs may be mapped to aPRB in a frequency-first mapping rule in the PRB, as illustrated in FIG.38. However, the mapping pattern may vary according to an actual REGconfiguration and actual indexing.

As one method, frequency-first mapping may be performed across totalR-PDCCH PRBs. Then an interleaved result may be obtained as illustratedin FIG. 39. In FIG. 39, CCE0 and CCE4 exist in R-PDCCH PRBs #0 and #4only. Each CCE is present only in an R-PDCCH PRB with an indexcorresponding to the CCE. Therefore, a diversity gain problem may occur.If the VRB size is different from the PRB size, mapping may be performedin a different manner.

As another method, time-first mapping may be performed within eachR-PDCCH PRB. FIG. 40 illustrates an example of time-first mapping.

Interleaving and mapping method 2 is almost identical to the method ofFIG. 38 in terms of transmission. However, an RN should additionallyperform blind decoding according to interleaving depths in order todetect an interleaving depth because the RN does not know how many RBsare used for interleaving. However, this method can dynamically optimizeresources by setting an interleaving depth equal to the size of anR-PDCCH to be transmitted (e.g. a RB unit), when possible. If theinterleaving depth is 1 RB, the size of an R-PDCCH for actualtransmission may be equal to the actual interleaving depth. Notably, itis desirable to preset interleaving depths in units of a predeterminedsize, such as 4 RBs, 8 RBs, 12 RBs, etc. in order to reduce the numberof operations of blind decoding for interleaving depths. Thisinformation may be set by RRC signaling. If an R-PDCCH area includes 16RBs and an interleaving depth of only {8 RBs, 16 RBs} is permitted, oneof various sets such as {4 RBs, 8 RBs, 16 RBs}, {4 RBs, 8 RBs, 12 RBs,16 RBs}, and {4 RBs, 16 RBs} may be preset by signaling.

This signaling scheme may be used when an RN determines a monitoring setin Method 3. That is, one of set 1, set 2 and even full sets may besignaled to an RN, as an appropriate monitoring set. This scheme can beused to signal an RN monitoring set in almost all proposed methods.

Methods 1, 2 and 3 are based on the assumption of a fixed interleavercolumn size. However, the fixed interleaver column size is purelyexemplary and the column size may be variable. For instance,interleaving may be performed in an interleaver with a column size of16.

RN-Specific CCE Indexing

The foregoing methods have been described on the premise that CCEindexes are cell-specific. Unlike this, CCE indexes may be definedRN-specifically. In FIG. 38, CCE0 to CCE3 and CCE4 to CCE7 areRN-specifically interleaved separately and it is assumed that eachinterleaving group includes CCE0 to CCE3. As a result, CCE0 of group 1is different from CCE0 of group 2. Only when information required todistinguish them is signaled to an RN, the RN may calculate BS-specific(or cell-specific) CCE indexes. Since BS-specific CCE indexes are usedto determine RN PUCCH resources during UL ACK/NACK transmission, theyshould be defined cell-specifically to avoid overlapped RA or resourcewaste. Instead of additionally transmitting information such as a groupindex for RN PUCCH resources, the RN PUCCH resources (e.g. PUCCH RBs)may be allocated by group and the start RB of the allocated RN PUCCHresources may be signaled. For reference, RN PUCCH resources are assumedto be linked with an R-PDCCH CCE index (e.g. a minimum CCE index for anR-PDCCH).

Interleaving and Mapping Method 4

FIG. 41 illustrates an R-PDCCH mapping operation in Method 4. Accordingto Method 4, permutation is uniformly performed (e.g. using bitreversal) during VRB-to-PRB mapping, without performing column-wisepermutation during interleaving. In this method, an interleaver columnsize is defined as the number of REGs in a CCE and an interleaver rowsize is changed according to the number of CCEs to be interleaved.According to this method, REGs constituting one VRB are extracted from 8different CCEs (herein, 1 VRB=8 REGs). If the number of R-PDCCH RRBs isnot 2^(N) (N=1, 2, 3, . . .), mapping may be performed by bit reversalpruning The interleaver column size characteristic of this method isalso applicable to Methods 1,2 and 3.

Interleaving and Mapping Method 5

FIG. 42 illustrates an R-PDCCH mapping operation in Method 5. Accordingto Method 5, column-wise permutation is performed during interleavingand a simple mapping rule is used for VRB-to-PRB mapping withoutpermutation (e.g. bit reversal). Equation 4 is also applicable to Method5. In this method, an interleaver column size is defined as the numberof REGs in a CCE and an interleaver row size is changed according to thenumber of CCEs to be interleaved.

R-PDCCH PRB Mapping Rule

In an interleaving mode, interleaving outputs or VRBs may be mapped toR-PDCCH PRBs using a DVRB RA rule. For example, PRB indexes 0, 1, 9, 10,18, 19, 27, and 28 (subset#0) may be used for R-PDCCH PRBs in FIG. 43.While R-PDCCHs may be transmitted in arbitrary positions throughsignaling (e.g. bitmap), a multiplexing rule compatible with aconventional RA method is desirably used in consideration of RAefficiency. For instance, a DVRB rule may be used to map R-PDCCHinterleaver outputs or R-PDCCH VRBs to PRBs. Assuming that aninterleaver size is, for example, 4 RBs, PRB indexes 0, 9, 18, and 27are interleaved. If 8 RBs are interleaved, PRB indexes 0, 1, 9, 10, 18,19, 27, and 28 are joint-interleaved. If a maximum interleaving size is4 RBs, PRBs #0, 9, 18, and 27 belong to RN interleaving group#1 and PRBs#1, 10, 19, and 28 correspond to RN interleaving group#2.

If it is desired to keep an interval between interleaving groupsuniform, PRBs in a contiguous subset or PRBs in a different subset suchas PRB #3, 12, 21, and 30 may be designated for interleaving group#2.This method is similar to separate designation of PRBs used for aninterleaving group on a subset basis.

Meanwhile, specific consideration for RA is needed to match the firstslot and the second slot in the interleaving mode (i.e. to allocateresources to a PRB pair on the same frequency). For example, while VRBindexes 0 to 3 or 0 to 7 are allocated to PRB pairs as intended, VRBindexes including nulls or contiguous 4RBs which are not a multiple of 4may not be configured with PRB pairs. Accordingly, R-PDCCHs should notreside in such positions. FIG. 44 illustrates an example of incorrectlyconfiguring an R-PDCCH SS. FIG. 45 illustrates an example of correctingthe configuration of the R-PDCCH SS of FIG. 44.

Obviously, since only a PRB index of the first slot is meaningful in anon-interleaving mode, the configuration of the R-PDCCH SS of FIG. 4does not matter.

R-PDCCH SS PRB Configuration Considering RBG

In the case of R-PDCCH SS configuration on an RBG basis (for reference,units other than an RBG may be defined for an R-PDCCH SS). Aconfiguration order of SS PRBs in an RBG according to increase of anaggregation level is proposed.

FIG. 46 illustrates an example of R-PDCCH SS configuration according toan aggregation level.

Referring to FIG. 46, an R-PDCCH SS may be configured with one PRB perRBG in aggregation level 1. The positions of SS PRBs in an RBG may bedetermined according to a preset rule (e.g. the largest RB index in anRBG) (a). In the case of aggregation level 2, 2 PRBs in an RBG areselected using PRB indexes in the RBG, starting sequentially from aspecific PRB. If the number of SS PRBs exceeds the number of PRB indexesin an RBG, SS PRBs may be determined using the concept of cyclicindexes. For example, if PRBs in an RBG are sequentially allocated to SSPRBs, starting from the last PRB, in the case of aggregation level 2, aPRB having the largest index in the RBG is allocated first to SS PRBsand then a PRB having the smallest index in the RBG is allocated to theSS PRBs (b). A descending order as well as an ascending order may beused as the indexing order. The most significant feature herein is an SSPRB configuration method in the case of an aggregation level of 4 ormore. If the number of SS PRBs according to an aggregation level exceedsthe number of PRBs in an RBG, SS PRBs are sequentially configured in anRBG by the aforementioned scheme and then skipped to PRBs of another RBGso that SS PRBs of another PBG in aggregation level 1 may be included inSS PRBs in aggregation level 4. In FIG. 46, indication lines betweenPRBs in an RBG shows an SS PRB configuration order.

FIG. 47 illustrates a method of limiting the number of R-PDCCH PRBswhich can be configured for an SS in an RBG. If a limited value is setto 2, a maximum of two PRBs per RBG is designated as SS PRBs and thusone R-PDCCH is configured in two RBGs.

FIG. 48 illustrates a BS, an RN, and a UE which are applicable to thepresent invention.

Referring to FIG. 48, a wireless communication system includes a BS110,an RN 120, and a UE 130.

The BS110 includes a processor 112, a memory 114, and an RF unit 116.The processor 112 may be configured so as to implement the proceduresand/or methods of the present invention. The memory 114 is connected tothe processor 112 and stores various pieces of information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives RF signals. The RN 120includes a processor 122, a memory 124, and an RF unit 126. Theprocessor 122 may be configured so as to implement the procedures and/ormethods of the present invention. The memory 124 is connected to theprocessor 122 and stores various pieces of information related tooperations of the processor 122. The RF unit 126 is connected to theprocessor 122 and transmits and/or receives RF signals. The UE 130includes a processor 132, a memory 134, and an RF unit 136. Theprocessor 132 may be configured so as to implement the procedures and/ormethods of the present invention. The memory 134 is connected to theprocessor 132 and stores various pieces of information related tooperations of the processor 132. The RF unit 136 is connected to theprocessor 132 and transmits and/or receives RF signals. The BS110, theRN 120, and/or the UE 130 may have a single antenna or multipleantennas.

The embodiments of the present invention described hereinabove arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in the embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obviousthat claims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentinvention or included as a new claim by subsequent amendment after theapplication is filed.

In this document, the embodiments of the present invention have beendescribed centering on a data transmission and reception relationshipamong a UE, a BS, and an RN. In some cases, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term BS may be replaced with the termsfixed station, Node B, eNode B (eNB), access point, etc. The term UE maybe replaced with the term Mobile Station (MS), Mobile Subscriber Station(MSS), etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a com theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs) , Digital Signal Processing Devices (DSPDs) ,Programmable Logic Devices (PLDs) , Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

The present invention relates to a wireless communication system.Particularly, the present invention is applicable to a method andapparatus for allocating resources for a physical channel to an RN.

What is claimed is:
 1. A method of transmitting a Relay PhysicalDownlink Control Channel (R-PDCCH) at a base station in a wirelesscommunication system, the method comprising: assigning a set of VirtualResource Blocks (VRBs) for the R-PDCCH to a downlink subframe; andtransmitting the downlink subframe to a relay node; wherein the set ofVRBs is configured to be same, by higher layer, in a first slot and asecond slot of the downlink subframe, and wherein if the set of VRBs forthe R-PDCCH is assigned in the first slot of the downlink subframe, theR-PDCCH is configured to contain a downlink assignment, and wherein ifthe set of VRBs for the R-PDCCH is assigned in the second slot of thedownlink subframe, the R-PDCCH is configured to contain an uplink grant.2. The method of claim 1, wherein the set of VRBs is indicated to therelay node by higher layer signalling
 3. The method of claim 2, whereinthe higher layer signalling is Radio Resource Control (RRC) signalling.4. The method of claim 2, wherein the set of VRBs is represented by abitmap.
 5. The method of claim 1 wherein the R-PDCCH is not interleaved.6. The method of claim 5, wherein the set of VRBs is configured to bedistributed VRBs (DVRBs).
 7. The method of claim 6, wherein the set ofVRBs are distributed to one or more Physical Resource Blocks (PRBs) inthe first slot, and the set of VRBs are distributed to one or more PRBsin the second slot, wherein the distribution to the one or more PRBs inthe second slot is configured to have at least one identical PRB indexwith the one or more PRBs in the first slot.
 8. A method of receivingRelay Physical Downlink Control Channel (R-PDCCH) at a relay in awireless communication system, the method comprising: receiving asubframe, starting from a specific Orthogonal Frequency DivisionMultiplexing (OFDM) symbol other than a first OFDM symbol of thesubframe; monitoring a first VRB set in a first slot of the subframe fora first R-PDCCH containing a downlink assignment; and monitoring asecond VRB set in a second slot of the subframe for a second R-PDCCHcontaining an uplink assignment, wherein the first VRB set and thesecond VRB set are configured to be same VRB set in accordance with asingle VRB set for R-PDCCH configured by higher layers.